# The 30 largest IT Services and IT Consulting companies in the Hauts-de-Seine department

Tamtam tracks 706 IT Services and IT Consulting companies headquartered in the Hauts-de-Seine department. This list ranks the 30 largest by number of employees on LinkedIn, led by VINCI Energies, Altran and Econocom. Their median headcount is 2,115. Half of them were founded in 1987 or later. The most common headquarters are Nanterre (6), Boulogne-Billancourt (5) and Neuilly-sur-Seine (3).

The Hauts-de-Seine department hosts a significant cluster of IT services and consulting firms, predominantly large groups. These companies offer a wide range of digital transformation solutions, from infrastructure management to cybersecurity and specialized engineering.

Key players include VINCI Energies, which focuses on multi-technical solutions for environmental transition, and Econocom, providing equipment and managed services for digital transformation. Orange Cyberdefense specializes in cybersecurity, while Cegedim offers technology and services for healthcare data management. Many of these firms, such as CS GROUP and Apside, were founded between the late 1960s and early 1990s, indicating a mature and established sector.

🇫🇷 Hauts-de-Seine · 30 companies · Updated Nov 15, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [VINCI Energies](https://www.tamtam.ai/c/vinci-energies) (vinci-energies.com)<br>Contributes to environmental transition by implementing customized multi-technical solutions from design to maintenance, enhancing infrastructure reliability, efficiency, and sustainability for energy and digital sectors. | IT Services and IT Consulting | 🇫🇷 Nanterre | 25,848 |  |
| 2 | [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 |  |
| 3 | [Econocom](https://www.tamtam.ai/c/econocom) (econocom.com)<br>Supplies, finances, and provides managed services for workplace, audiovisual, and infrastructures, supporting businesses in their digital transformation with equipment and support. | IT Services and IT Consulting | 🇫🇷 Puteaux | 7,123 | 1973 |
| 4 | [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 |
| 5 | [OPEN](https://www.tamtam.ai/c/open-levallois-perret) (open.global)<br>Supports large companies and public organizations in digital transformation, focusing on technological performance, sovereignty, digital sobriety, and scaling innovations with advanced solutions. | IT Services and IT Consulting | 🇫🇷 Levallois-Perret | 4,705 | 1989 |
| 6 | [APC by Schneider Electric](https://www.tamtam.ai/c/apc-by-schneider-electric) (apc.com)<br>Provides reliable, efficient, connected, and innovative products for IT equipment, ensuring accessibility and security for dynamic IT in a connected world. | IT Services and IT Consulting | 🇫🇷 Rueil-Malmaison | 4,378 | 1981 |
| 7 | [Orange Cyberdefense](https://www.tamtam.ai/c/orange-cyberdefense) (orangecyberdefense.com)<br>Expert cybersecurity business unit of the Orange Group. They are a leading security provider, striving to build a safer digital society. | IT Services and IT Consulting | 🇫🇷 Nanterre | 4,274 |  |
| 8 | [Axians](https://www.tamtam.ai/c/axians) (axians.com)<br>A technology company supporting digital transformation by providing ICT solutions in cybersecurity, telecommunication, data analytics, cloud services, and more | IT Services and IT Consulting | 🇫🇷 Nanterre | 4,186 |  |
| 9 | [Cegedim](https://www.tamtam.ai/c/cegedim) (cegedim.com)<br>Technology and services for digital data flow management in healthcare ecosystems and B2B, plus business software publishing for healthcare and insurance professionals. | IT Services and IT Consulting | 🇫🇷 Boulogne-Billancourt | 4,103 | 1969 |
| 10 | [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 |
| 11 | [CS GROUP](https://www.tamtam.ai/c/cs-group) (cs-soprasteria.com)<br>Designs, builds, deploys, and maintains critical systems with innovative solutions and products, ensuring operational efficiency and security for client missions. | IT Services and IT Consulting | 🇫🇷 Le Plessis Robinson | 2,968 | 1968 |
| 12 | [SPIE ICS](https://www.tamtam.ai/c/spie-ics) (spie.fr)<br>Supports digital transformation for businesses with ICT solutions, providing expertise in IT infrastructure, cloud, cybersecurity, and data & IoT for enhanced performance and user well-being. | IT Services and IT Consulting | 🇫🇷 Malakoff | 2,930 | 2001 |
| 13 | [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 |
| 14 | [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 |
| 15 | [HELPLINE](https://www.tamtam.ai/c/helpline) (helpline.fr)<br>Specialized in user support outsourcing, AI-enhanced employee experience, and IT asset management. Supports IT departments and offers seamless employee experience. | IT Services and IT Consulting | 🇫🇷 Nanterre | 2,115 | 1994 |
| 16 | [Berger-Levrault](https://www.tamtam.ai/c/berger-levrault) (berger-levrault.com)<br>Provides software solutions for public sector, healthcare, education, and industry, focusing on HR, financial management, and maintenance management for global customers. | IT Services and IT Consulting | 🇫🇷 Boulogne-Billancourt | 2,064 | 1676 |
| 17 | [Infotel](https://www.tamtam.ai/c/infotel) (infotel.com)<br>Provides IT and digital transformation consulting for large enterprises, focusing on strategic design, technological expertise, and agile development, from conception to implementation. | IT Services and IT Consulting | 🇫🇷 Neuilly-sur-Seine | 1,894 | 1979 |
| 18 | [Extia](https://www.tamtam.ai/c/extia) (extia-group.com)<br>Offers IT consulting services across various sectors, focusing on employee well-being to drive project success and client performance with a collaborative approach. | IT Services and IT Consulting | 🇫🇷 Sèvres | 1,881 | 2007 |
| 19 | [Sofrecom](https://www.tamtam.ai/c/sofrecom) (sofrecom.com)<br>Advises, guides, and supports telecommunications players' digital transformation and green transition, offering business, network, and IT consulting for improved operational performance. | IT Services and IT Consulting | 🇫🇷 Châtillon | 1,469 | 1966 |
| 20 | [Niji](https://www.tamtam.ai/c/niji) (niji.fr)<br>Provides consulting, design, and technology implementation for digital transformation in businesses and public organizations, including Salesforce integration and cybersecurity. | IT Services and IT Consulting | 🇫🇷 Issy-les-Moulineaux | 1,460 | 2001 |
| 21 | [SCC France](https://www.tamtam.ai/c/scc-france) (scc.com)<br>Provides comprehensive IT solutions, including cybersecurity, digital workplace, and hybrid infrastructure, enabling businesses to optimize operations and achieve their goals. | IT Services and IT Consulting | 🇫🇷 Nanterre | 1,422 | 1975 |
| 22 | [NXO France](https://www.tamtam.ai/c/nxo-france) (nxo.eu)<br>Independent leader in French Telecom integration, undertaking complex projects, anticipating customer needs, attracting talent, and focusing on well-done work. | IT Services and IT Consulting | 🇫🇷 Puteaux | 1,200 |  |
| 23 | [Axians France](https://www.tamtam.ai/c/axians-france) (axians.fr)<br>Supports clients with digital infrastructure and solutions, covering applications, data, networks, cloud, telecom, and cybersecurity through consulting, design, integration, and services. | IT Services and IT Consulting | 🇫🇷 Nanterre | 1,137 | 1999 |
| 24 | [SFEIR](https://www.tamtam.ai/c/sfeir) (sfeir.com)<br>Provides expert application development across web, mobile, cloud, data, and IoT, guiding clients through digital transformation with innovative products. | IT Services and IT Consulting | 🇫🇷 Neuilly-sur-Seine | 1,083 | 1985 |
| 25 | [CDC Informatique](https://www.tamtam.ai/c/cdc-informatique) (icdc.caissedesdepots.fr)<br>Provides IT solutions, guarantees security and integrity for public sector clients. Technological competence and innovation are key, anticipating and supporting digital changes. | IT Services and IT Consulting | 🇫🇷 Bagneux | 1,049 | 1959 |
| 26 | [Klee Group](https://www.tamtam.ai/c/klee-group) (kleegroup.com)<br>Design and deliver tailored digital business solutions, supporting clients throughout their digital project lifecycle with a comprehensive range of expertise. | IT Services and IT Consulting | 🇫🇷 Le Plessis Robinson | 1,025 | 1987 |
| 27 | [SOFTEAM](https://www.tamtam.ai/c/softeam) (softeam.com)<br>Accompanying transformations long-term; imagining, designing, operating future services; combining consulting, digital solutions, and service excellence for various sectors, leveraging over 1,650 experts. | IT Services and IT Consulting | 🇫🇷 Courbevoie | 1,003 | 1989 |
| 28 | [Randstad Digital France](https://www.tamtam.ai/c/randstad-digital-france) (randstaddigital.fr)<br>Provides global talent, production capabilities, and specialized solutions to rapidly transform businesses through expertise in customer experience, engineering, data, and cloud. | IT Services and IT Consulting | 🇫🇷 Issy-les-Moulineaux | 987 |  |
| 29 | [AUSY](https://www.tamtam.ai/c/ausy) (ausy.fr)<br>A leading European provider of high-tech consulting and engineering solutions, combining creativity, technology, and human touch to drive technological transformations globally | IT Services and IT Consulting | 🇫🇷 Sèvres | 970 |  |
| 30 | [ACENSI](https://www.tamtam.ai/c/acensi) (acensi.fr)<br>Supports clients through IS transformation projects, including digital transformation, Big Data, mobility, cloud, security, and cybersecurity from design to implementation. | IT Services and IT Consulting | 🇫🇷 Courbevoie | 848 | 2003 |

## 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 15, 2026.

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- [IT Services and IT Consulting companies in the Rhône department](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-rhone) (253)
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- [IT Services and IT Consulting companies in Grand Est](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-grand-est) (214)
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Source: https://www.tamtam.ai/l/it-services-and-it-consulting-companies-hauts-de-seine