# Top 30 professional services firms in the Hauts-de-Seine department

Tamtam tracks 629 professional services firms headquartered in the Hauts-de-Seine department. This list ranks the 30 largest by number of employees on LinkedIn, led by ALTEN, ELIS and Altran. Their median headcount is 4,173. Half of them were founded in 1988 or later. The most common headquarters are Boulogne-Billancourt (6), Neuilly-sur-Seine (5) and Courbevoie (4).

The companies listed in Hauts-de-Seine are primarily large professional services firms, with a strong emphasis on engineering, IT consulting, and environmental services. These companies provide specialized expertise across various industries, from digital transformation to risk management.

Among them, ALTEN provides engineering and IT services, ELIS offers circular services for hygiene and well-being, Equans France designs solutions for energy and digital transitions, and Devoteam specializes in AI-driven tech consulting. Many of these firms, such as Apave and ELIS, have long histories, indicating established players in their respective fields. The presence of multiple headquarters in Boulogne-Billancourt, Courbevoie, and Levallois-Perret suggests these cities are significant hubs for professional services within the department.

🇫🇷 Hauts-de-Seine · 30 companies · Updated Nov 12, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [ALTEN](https://www.tamtam.ai/c/alten) (alten.com)<br>Provides engineering and IT services, supporting businesses in technological and sustainable transformation across various industries with high-level consultant-engineers. | Engineering Services | 🇫🇷 Boulogne-Billancourt | 38,710 | 1988 |
| 2 | [ELIS](https://www.tamtam.ai/c/elis-puteaux) (elis.com)<br>A global provider of circular services for hygiene and well-being, offering solutions for various sectors while promoting environmental sustainability and customer focus | Facilities Services | 🇫🇷 Puteaux | 15,750 | 1883 |
| 3 | [Altran](https://www.tamtam.ai/c/altran) (capgemini-engineering.com)<br>Altran, now Capgemini Engineering, offers engineering services Follow them on LinkedIn for updates and insights | IT Services and IT Consulting | 🇫🇷 Neuilly-sur-Seine | 11,652 |  |
| 4 | [Equans France](https://www.tamtam.ai/c/equans-france) (equans.fr)<br>Designs, installs, and delivers bespoke solutions optimizing equipment and usage for businesses, local authorities, and industrial players in energy, industrial, and digital transitions. | Environmental Services | 🇫🇷 Courbevoie | 11,029 | 2021 |
| 5 | [Devoteam](https://www.tamtam.ai/c/devoteam) (devoteam.com)<br>AI-driven tech consulting firm specializing in cloud platforms, cyber, data, and sustainability, guiding businesses through sustainable digital transformation to deliver value. | Business Consulting and Services | 🇫🇷 Levallois-Perret | 10,274 |  |
| 6 | [Apave](https://www.tamtam.ai/c/apave) (apave.com)<br>Specializes in technical, human, environmental, and digital risk management, ensuring safety and performance across various economic sectors for over 150 years. | Environmental Services | 🇫🇷 Courbevoie | 9,778 | 1867 |
| 7 | [Forvis Mazars Group](https://www.tamtam.ai/c/forvis-mazars-group) (forvismazars.com)<br>International partnership delivering audit, tax, and advisory services across one hundred countries and territories through an integrated global professional services network. | Accounting | 🇫🇷 Levallois-Perret | 9,534 |  |
| 8 | [Assystem](https://www.tamtam.ai/c/assystem) (assystem.com)<br>Independent nuclear engineering company accelerating energy transition, developing nuclear and renewable energies, power grids, hydrogen projects, and low-carbon transport. | Business Consulting and Services | 🇫🇷 Courbevoie | 8,143 |  |
| 9 | [Actemium](https://www.tamtam.ai/c/actemium) (actemium.com)<br>Delivering bespoke solutions and services globally, combining local business unit expertise to create value throughout the industrial life cycle for a sustainable world. | Automation Machinery Manufacturing | 🇫🇷 Nanterre | 6,718 |  |
| 10 | [Astek](https://www.tamtam.ai/c/astek) (astekgroup.fr)<br>Supports clients with high-value service, deep technical expertise across technology, operations, and engineering, focusing on sustainable digital transformation with humans at the core. | IT Services and IT Consulting | 🇫🇷 Boulogne-Billancourt | 6,035 | 1988 |
| 11 | [TRIGO](https://www.tamtam.ai/c/trigo) (trigo-group.com)<br>Provides comprehensive quality solutions and management services for automotive, aerospace, and transport industries, addressing supply chain challenges globally with local expertise. | Business Consulting and Services | 🇫🇷 Nanterre | 5,771 | 1997 |
| 12 | [Vulcain Engineering Group](https://www.tamtam.ai/c/vulcain-engineering-group) (vulcain-eng.com)<br>Provides engineering consulting and project solutions for energy and environmental sectors, delivering technical assistance, expertise, and project management globally. | Business Consulting and Services | 🇫🇷 Neuilly-sur-Seine | 5,234 | 2005 |
| 13 | [Securitas France](https://www.tamtam.ai/c/securitas-france) (securitas.fr)<br>Provides private security services including surveillance and guarding, tailored to meet specific business security needs and requirements. | Security and Investigations | 🇫🇷 Issy-les-Moulineaux | 5,060 |  |
| 14 | [Synergie France](https://www.tamtam.ai/c/synergie-france) (synergie.fr)<br>French leader in HR services: recruitment, training, and HR consulting Providing solutions in various sectors, emphasizing proximity, performance, and diversity | Human Resources Services | 🇫🇷 Boulogne-Billancourt | 4,804 |  |
| 15 | [BNP Paribas Real Estate](https://www.tamtam.ai/c/bnp-paribas-real-estate) (bnpparibas.com)<br>Offers comprehensive real estate services including property development, transactions, consulting, valuation, and property management across Europe, the Middle East, and Asia. | Real Estate | 🇫🇷 Boulogne-Billancourt | 4,173 | 1963 |
| 16 | [PwC France](https://www.tamtam.ai/c/pwc-france) (pwc.fr)<br>Offers consulting, audit, legal, and tax expertise, blending technology with multidisciplinary knowledge to accelerate sustainable business transformation for organizations. | Business Consulting and Services | 🇫🇷 Neuilly-sur-Seine | 4,109 |  |
| 17 | [Scalian](https://www.tamtam.ai/c/scalian) (scalian.com)<br>A global company founded in 1989 with 3 business lines focusing on Digital Transformation, Digital Systems, and Operations Performance across various countries | Business Consulting and Services | 🇫🇷 Neuilly-sur-Seine | 4,098 | 1989 |
| 18 | [Manpower France](https://www.tamtam.ai/c/manpower-france) (manpower.fr)<br>Offers recruitment solutions through a network of specialized consultants and provides flexible interim staffing solutions across various sectors to companies of all sizes. | Human Resources Services | 🇫🇷 Puteaux | 3,839 | 1957 |
| 19 | [Leyton](https://www.tamtam.ai/c/leyton) (leyton.com)<br>International consulting firm helps businesses leverage financial incentives for growth and long-lasting performance by simplifying access to complex benefits. | Business Consulting and Services | 🇫🇷 Issy-les-Moulineaux | 3,243 | 1997 |
| 20 | [Dekra France](https://www.tamtam.ai/c/dekra-france) (dekra.fr)<br>Inspection, certification, risk management, audits, training, and consulting services for automotive, transport, industry, environment, and safety sectors. | Environmental Services | 🇫🇷 Le Plessis Robinson | 3,188 | 1925 |
| 21 | [VISEO](https://www.tamtam.ai/c/viseo) (viseo.com)<br>Assists clients globally with digital and business transformation using advanced technology and industry expertise for productivity, innovation, and competitiveness. | IT Services and IT Consulting | 🇫🇷 Boulogne-Billancourt | 3,016 | 1999 |
| 22 | [VINCI Energies en France](https://www.tamtam.ai/c/vinci-energies-en-france)<br>Accelerating environmental transition in France by focusing on energy and digital transformations for factories, buildings, cities, and energy/transport infrastructure with innovative solutions | Environmental Services | 🇫🇷 Nanterre | 2,953 |  |
| 23 | [SE Advisory Services](https://www.tamtam.ai/c/se-advisory-services) (seadvisoryservices.com)<br>Helps organizations achieve sustainability, energy, and digitalization goals through expertise, global implementation, and AI-powered software, turning challenges into advantages. | Business Consulting and Services | 🇫🇷 Rueil-Malmaison | 2,948 |  |
| 24 | [SQLI](https://www.tamtam.ai/c/sqli) (sqli.com)<br>Leading European group for customer experience and digital transformation services. Empowering international brands with digital innovation, combining technology, methodologies, and AI for business growth. | IT Services and IT Consulting | 🇫🇷 Levallois-Perret | 2,854 | 1990 |
| 25 | [Vitalliance](https://www.tamtam.ai/c/vitalliance) (vitalliance.fr)<br>Provides comprehensive home care support for individuals experiencing loss of autonomy, assisting with daily living, administrative tasks, and social interaction, including inclusive housing projects. | Individual and Family Services | 🇫🇷 Courbevoie | 2,702 | 2003 |
| 26 | [Sogetrel](https://www.tamtam.ai/c/sogetrel) (sogetrel.fr)<br>A leader in digital transformation, specializing in digital infrastructure services and connected devices to enhance citizens' lives, business performance, and sustainable development | Telecommunications | 🇫🇷 Issy-les-Moulineaux | 2,581 | 1985 |
| 27 | [UFF - Conseil en gestion de patrimoine](https://www.tamtam.ai/c/uff-conseil-en-gestion-de-patrimoine) (uff.net)<br>Established in 1968, this bank provides wealth management services for individuals, businesses, executives, and professional athletes Offers a range of financial products and solutions | Financial Services | 🇫🇷 Bois-Colombes | 2,466 | 1968 |
| 28 | [Grant-Thornton France](https://www.tamtam.ai/c/grant-thornton-france) (grantthornton.fr)<br>Provides audit, financial advisory, operational consulting, legal and tax advice, and sustainable transformation services to French businesses. | Financial Services | 🇫🇷 Neuilly-sur-Seine | 2,342 | 1964 |
| 29 | [Apside](https://www.tamtam.ai/c/apside) (apside.com)<br>Provides consulting, engineering in Information Systems, Technical and Scientific Computing, Automotive and Financial Engineering, for large French and European groups. | IT Services and IT Consulting | 🇫🇷 Boulogne-Billancourt | 2,300 | 1976 |
| 30 | [NUVIA](https://www.tamtam.ai/c/nuvia) (nuvia.com)<br>International company provides engineering, products, and support services for highly regulated industrial sites, including nuclear, defense, health, and environment sectors. | Construction | 🇫🇷 Rueil-Malmaison | 2,281 | 2007 |

## How this list is built

Every company on this list has a Tamtam company profile. The industry is the one the company gives on LinkedIn; categories such as SaaS or fintech are classified by Tamtam's AI from the company's website and LinkedIn page; and the headquarters city must match the company's own address. Companies are ranked by the number of employees on LinkedIn, and the list is refreshed every night. Classifications can be wrong, so treat the list as a starting point rather than an official ranking. Last updated Nov 12, 2026.

## More company lists in the Hauts-de-Seine department

- [The largest companies in the Hauts-de-Seine department](https://www.tamtam.ai/l/largest-companies-hauts-de-seine) (5,160)
- [Multinational companies in the Hauts-de-Seine department](https://www.tamtam.ai/l/multinational-companies-hauts-de-seine) (1,231)
- [IT services companies in the Hauts-de-Seine department](https://www.tamtam.ai/l/it-services-companies-hauts-de-seine) (737)
- [IT Services and IT Consulting companies in the Hauts-de-Seine department](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-hauts-de-seine) (706)
- [Consulting firms in the Hauts-de-Seine department](https://www.tamtam.ai/l/consulting-firms-hauts-de-seine) (563)
- [Companies with in-house R&D in the Hauts-de-Seine department](https://www.tamtam.ai/l/r-and-d-companies-hauts-de-seine) (510)
- [SaaS companies in the Hauts-de-Seine department](https://www.tamtam.ai/l/saas-companies-hauts-de-seine) (389)
- [Business Consulting and Services companies in the Hauts-de-Seine department](https://www.tamtam.ai/l/business-consulting-and-services-companies-hauts-de-seine) (304)
- [Software Development companies in the Hauts-de-Seine department](https://www.tamtam.ai/l/software-development-companies-hauts-de-seine) (301)
- [Retail chains in the Hauts-de-Seine department](https://www.tamtam.ai/l/retail-chains-hauts-de-seine) (292)
- [Manufacturers in the Hauts-de-Seine department](https://www.tamtam.ai/l/manufacturers-hauts-de-seine) (285)
- [Advertising Services companies in the Hauts-de-Seine department](https://www.tamtam.ai/l/advertising-services-companies-hauts-de-seine) (281)
- [Marketing and communications agencies in the Hauts-de-Seine department](https://www.tamtam.ai/l/marketing-agencies-hauts-de-seine) (235)
- [Subscription businesses in the Hauts-de-Seine department](https://www.tamtam.ai/l/subscription-businesses-hauts-de-seine) (228)
- [Hardware manufacturers in the Hauts-de-Seine department](https://www.tamtam.ai/l/hardware-companies-hauts-de-seine) (199)
- [Financial services firms in the Hauts-de-Seine department](https://www.tamtam.ai/l/financial-services-firms-hauts-de-seine) (198)
- [Companies with a mobile app in the Hauts-de-Seine department](https://www.tamtam.ai/l/companies-with-mobile-app-hauts-de-seine) (189)
- [Critical infrastructure operators in the Hauts-de-Seine department](https://www.tamtam.ai/l/critical-infrastructure-operators-hauts-de-seine) (169)
- [AI companies in the Hauts-de-Seine department](https://www.tamtam.ai/l/ai-companies-hauts-de-seine) (159)
- [Education providers in the Hauts-de-Seine department](https://www.tamtam.ai/l/education-companies-hauts-de-seine) (159)
- [Cybersecurity companies in the Hauts-de-Seine department](https://www.tamtam.ai/l/cybersecurity-companies-hauts-de-seine) (154)
- [Distributors and wholesalers in the Hauts-de-Seine department](https://www.tamtam.ai/l/distributors-and-wholesalers-hauts-de-seine) (154)
- [Recruitment and staffing agencies in the Hauts-de-Seine department](https://www.tamtam.ai/l/recruitment-agencies-hauts-de-seine) (152)
- [Energy companies in the Hauts-de-Seine department](https://www.tamtam.ai/l/energy-companies-hauts-de-seine) (144)

## The same list elsewhere in France

- [Professional services firms in France](https://www.tamtam.ai/l/professional-services-firms-france) (6,610)
- [Professional services firms in Île-de-France](https://www.tamtam.ai/l/professional-services-firms-ile-de-france) (3,377)
- [Professional services firms in Auvergne-Rhône-Alpes](https://www.tamtam.ai/l/professional-services-firms-auvergne-rhone-alpes) (711)
- [Professional services firms in Provence-Alpes-Côte d'Azur](https://www.tamtam.ai/l/professional-services-firms-provence-alpes-cote-dazur) (433)
- [Professional services firms in the Rhône department](https://www.tamtam.ai/l/professional-services-firms-rhone) (400)
- [Professional services firms in Occitanie](https://www.tamtam.ai/l/professional-services-firms-occitanie) (399)
- [Professional services firms in Grand Est](https://www.tamtam.ai/l/professional-services-firms-grand-est) (316)
- [Professional services firms in Nouvelle-Aquitaine](https://www.tamtam.ai/l/professional-services-firms-nouvelle-aquitaine) (308)
- [Professional services firms in Hauts-de-France](https://www.tamtam.ai/l/professional-services-firms-hauts-de-france) (260)
- [Professional services firms in Pays de la Loire](https://www.tamtam.ai/l/professional-services-firms-pays-de-la-loire) (253)
- [Professional services firms in the Bouches-du-Rhône department](https://www.tamtam.ai/l/professional-services-firms-bouches-du-rhone) (249)
- [Professional services firms in the Haute-Garonne department](https://www.tamtam.ai/l/professional-services-firms-haute-garonne) (208)
- [Professional services firms in the Nord department](https://www.tamtam.ai/l/professional-services-firms-nord) (178)
- [Professional services firms in Brittany](https://www.tamtam.ai/l/professional-services-firms-brittany) (167)
- [Professional services firms in the Loire-Atlantique department](https://www.tamtam.ai/l/professional-services-firms-loire-atlantique) (158)
- [Professional services firms in the Gironde department](https://www.tamtam.ai/l/professional-services-firms-gironde) (151)
- [Professional services firms in Normandy](https://www.tamtam.ai/l/professional-services-firms-normandy) (114)
- [Professional services firms in the Yvelines department](https://www.tamtam.ai/l/professional-services-firms-yvelines) (108)
- [Professional services firms in the Ille-et-Vilaine department](https://www.tamtam.ai/l/professional-services-firms-ille-et-vilaine) (94)
- [Professional services firms in Paris](https://www.tamtam.ai/l/professional-services-firms-paris) (2,241)
- [Professional services firms in Lyon](https://www.tamtam.ai/l/professional-services-firms-lyon) (265)
- [Professional services firms in Toulouse](https://www.tamtam.ai/l/professional-services-firms-toulouse) (139)
- [Professional services firms in Marseille](https://www.tamtam.ai/l/professional-services-firms-marseille) (123)
- [Professional services firms in Boulogne-Billancourt](https://www.tamtam.ai/l/professional-services-firms-boulogne-billancourt) (102)

## The same list elsewhere

- [Professional services firms in the world](https://www.tamtam.ai/l/professional-services-firms-in-the-world) (24,737)
- [Professional services firms in Europe](https://www.tamtam.ai/l/professional-services-firms-in-europe) (13,698)

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Source: https://www.tamtam.ai/l/professional-services-firms-hauts-de-seine