# The 30 largest consulting firms in the Seine-Saint-Denis department

Tamtam tracks 44 consulting firms headquartered in the Seine-Saint-Denis department. This list ranks the 30 largest by number of employees on LinkedIn, led by ARKANCE, Veolia | Engineering & Consulting and Veolia | Énergie & Décarbonation. Their median headcount is 60. Half of them were founded in 2005 or later. The most common headquarters are Saint-Denis (6), Montreuil (5) and Noisy-le-Grand (4).

These companies are primarily consulting firms located in the Seine-Saint-Denis department, with a notable presence in IT services, environmental consulting, and engineering. The list includes a mix of mid-sized firms and larger operations, such as ARKANCE, which provides digital transformation solutions, and Veolia, specializing in environmental services and energy decarbonation. CORELIA focuses on data correlation, while GIDEF offers professional reclassification support and competency assessments.

The data shows a concentration of these companies in cities like Saint-Denis, Montreuil, and Aubervilliers. Many of these firms, such as Cantor (software and data engineering) and GLI (technical engineering for smart buildings), were founded between the 1980s and early 2000s, indicating a mature and established consulting sector in the region.

🇫🇷 Seine-Saint-Denis · 30 companies · Updated Nov 12, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [ARKANCE](https://www.tamtam.ai/c/arkance) (arkance.world)<br>Provides digital transformation solutions and expert services for architecture, engineering, construction, and manufacturing industries, optimizing design, build, and manufacturing processes. | IT Services and IT Consulting | 🇫🇷 Saint-Denis | 679 |  |
| 2 | [Veolia \| Engineering & Consulting](https://www.tamtam.ai/c/veolia-engineering-and-consulting) (engineering-consulting.veolia.com)<br>Consulting engineering and strategic assistance division specializing in designing sustainable solutions for public, industrial, and tertiary sectors, focusing on resource management and performance improvement | Environmental Services | 🇫🇷 Aubervilliers | 436 |  |
| 3 | [Veolia \| Énergie & Décarbonation](https://www.tamtam.ai/c/veolia-energie-and-decarbonation) (veolia.fr)<br>Provides energy audits, renewable production, smart cooling networks, and performance optimization to ensure sovereignty and environmental footprint reduction for industries and local territories. | Environmental Services | 🇫🇷 Aubervilliers | 429 |  |
| 4 | [CORELIA](https://www.tamtam.ai/c/corelia) (corelia.ai)<br>CORELIA correlates data for clients, blending expertise with project complexity through IT and business alignment, emphasizing data's importance in all projects | IT Services and IT Consulting | 🇫🇷 Saint-Denis | 402 | 1985 |
| 5 | [GIDEF](https://www.tamtam.ai/c/gidef) (gidef.org)<br>A consulting firm offering professional reclassification support, engineering programs, competency assessments, education needs analysis, and social/economic studies for strategic decision-making | Professional Training and Coaching | 🇫🇷 Rosny-sous-Bois | 281 | 1994 |
| 6 | [Cantor](https://www.tamtam.ai/c/cantor) (cantor.fr)<br>Cantor is a computer service and engineering company specializing in software and data engineering, including big data processing within strict deadlines | Software Development | 🇫🇷 Neuilly-Plaisance | 250 | 1996 |
| 7 | [GLI](https://www.tamtam.ai/c/gli) (gli.fr)<br>Technical engineering and consultancy services for smart buildings focusing on energy efficiency, fire safety, cybersecurity, and electrical systems through project management and support. | Research Services | 🇫🇷 Montreuil | 250 | 1986 |
| 8 | [Dékuple](https://www.tamtam.ai/c/dekuple) (dekuple.com)<br>Family-owned group specializing in cross-channel data marketing, supporting large and mid-sized companies with turnkey creative marketing solutions. | Advertising Services | 🇫🇷 Montreuil | 207 | 1972 |
| 9 | [INTERCOM Technologies](https://www.tamtam.ai/c/intercom-technologies) (intercom-technologies.fr)<br>Specialized in high-value project expertise and management, supporting strategy, providing expert assistance, and operating nearshore agency for quality and growth. | Telecommunications | 🇫🇷 Rosny-sous-Bois | 197 | 2005 |
| 10 | [OGI - OMNIUM GÉNÉRAL D'INGENIERIE](https://www.tamtam.ai/c/ogi-omnium-general-d-ingenierie) (ogi2.fr)<br>OGI is a specialized engineering firm for public space development, offering a range of technical expertise for all aspects of project planning | Architecture and Planning | 🇫🇷 Montreuil | 190 | 1991 |
| 11 | [COTEBA](https://www.tamtam.ai/c/coteba) (arteliagroup.com)<br>European leader in engineering and project management, specializing in construction, infrastructure, and environment projects with a focus on professionalism, ethics, and sustainability | Construction | 🇫🇷 Saint-Denis | 154 | 1961 |
| 12 | [Calliope Business Solutions by TVH Consulting](https://www.tamtam.ai/c/calliope-business-solutions-by-tvh-consulting) (groupe-calliope.com)<br>Provides digital transformation through Microsoft and Sage ERP and CRM integration, utilizing packaged modules and structured methodology for retail, manufacturing, and services. | Software Development | 🇫🇷 Saint-Denis | 150 | 1995 |
| 13 | [Compagnie Francaise Informatique](https://www.tamtam.ai/c/compagnie-francaise-informatique) (cfigroupe.com)<br>A French leader in IT distribution and services for medium and large enterprises, evolving into a business solutions integrator with flexible payment options | IT Services and IT Consulting | 🇫🇷 Saint-Denis | 117 | 1981 |
| 14 | [GLOBAL PARTNER](https://www.tamtam.ai/c/global-partner) (global-partner.fr)<br>Audit, optimize, and manage telecommunication and printing solutions, combining negotiation, consulting, and technical expertise for best user experience. | IT Services and IT Consulting | 🇫🇷 Neuilly-Plaisance | 76 | 2010 |
| 15 | [SoftwareOne France](https://www.tamtam.ai/c/softwareone-france) (softwareone.com)<br>Global provider of software and cloud solutions, specializing in license lifecycle management, migration, modernization, and digital transformation support. | IT Services and IT Consulting | 🇫🇷 Saint-Ouen-sur-Seine | 60 |  |
| 16 | [ADENIS](https://www.tamtam.ai/c/adenis) (adenis.fr)<br>Innovative cybersecurity and IT services provider for small and medium-sized businesses, offering a competitive edge and future-oriented solutions to boost revenue | IT Services and IT Consulting | 🇫🇷 Bagnolet | 53 | 1999 |
| 17 | [InnovQube](https://www.tamtam.ai/c/innovqube) (innovqube.com)<br>Consulting and SaaS solutions specializing in cloud strategy, architecture optimization, security, automation, training, and digital transformation for businesses. | IT Services and IT Consulting | 🇫🇷 Noisy-le-Grand | 51 | 2024 |
| 18 | [AMOPRIM/AMODEV](https://www.tamtam.ai/c/amoprim-amodev) (amodev.eu)<br>Specialized in real estate project consulting for public actors, investors, and developers Services include auditing, project management, environmental assistance, and more | Real Estate | 🇫🇷 Montreuil | 49 | 2006 |
| 19 | [Wortis](https://www.tamtam.ai/c/wortis) (wortis.fr)<br>A Paris-based digital services company operating in system development, engineering, consulting, outsourcing, and telecommunications equipment across Europe and Africa | IT Services and IT Consulting | 🇫🇷 Bondy | 45 | 2014 |
| 20 | [Resadia](https://www.tamtam.ai/c/resadia) (resadia.com)<br>Network of regional businesses providing customized converged IP solutions including IT services, telecommunications, security, and hardware installation for companies of all sizes. | IT Services and IT Consulting | 🇫🇷 Pantin | 38 | 2006 |
| 21 | [Crisalyde](https://www.tamtam.ai/c/crisalyde) (crisalyde.fr)<br>A team of experienced consultants providing crisis preparation, management, training, and response services to both public and private sectors | Business Consulting and Services | 🇫🇷 Pantin | 34 | 2017 |
| 22 | [Team-X](https://www.tamtam.ai/c/team-x) (teamx.fr)<br>A team of web and digital enthusiasts since 2002, providing digital services to over 600 clients with a team of 50+ collaborators | IT Services and IT Consulting | 🇫🇷 Montreuil | 30 | 2002 |
| 23 | [Big Apps](https://www.tamtam.ai/c/big-apps) (bigapps.fr)<br>We are a team of 30+ data management specialists, providing consulting services in Data, DevOps, and Cloud to help clients optimize their digital transformation projects | IT Services and IT Consulting | 🇫🇷 Rosny-sous-Bois | 27 | 2014 |
| 24 | [Ceritek](https://www.tamtam.ai/c/ceritek) (ceritek.com)<br>Ceritek specializes in customer relations and unified communications, providing strategy, integration, and support to help companies enhance their customer experiences and loyalty | IT Services and IT Consulting | 🇫🇷 Noisy-le-Grand | 26 | 2005 |
| 25 | [ETIXWAY](https://www.tamtam.ai/c/etixway) (etixway.com)<br>A company specializing in digital transformation and Open Source, guiding clients in data analysis, IT systems evolution, and overall transformation success | IT Services and IT Consulting | 🇫🇷 Noisy-le-Grand | 24 |  |
| 26 | [ISTAV](https://www.tamtam.ai/c/istav) (istav.fr)<br>Private training and consulting organization specializing in urban wildlife expertise, hygiene, and risk management related to urban animal life in its various forms. | Professional Training and Coaching | 🇫🇷 Les Lilas | 21 | 2007 |
| 27 | [NEOFI Solutions](https://www.tamtam.ai/c/neofi-solutions) (neofi-solutions.com)<br>Consulting and integration services for financial flow management, cash management, and software deployment with a focus on interoperability and pragmatism. | Software Development | 🇫🇷 Saint-Denis | 20 | 2006 |
| 28 | [Groupe Fallyance](https://www.tamtam.ai/c/groupe-fallyance) (mallyance.fr)<br>Provides IT consulting, logistics solutions, infrastructure management, software development, and training with strong client and employee commitment. | IT Services and IT Consulting | 🇫🇷 Bagnolet | 20 | 2004 |
| 29 | [SPEEGAR](https://www.tamtam.ai/c/speegar)<br>Digital services consultancy specializing in Java and Angular web application development through collaborative methodologies to meet high technical standards for client projects. | Software Development | 🇫🇷 Noisy-le-Grand | 19 | 2019 |
| 30 | [Tisserand EC — Cabinet d'expertise comptable](https://www.tamtam.ai/c/tisserand-ec-cabinet-d-expertise-comptable) (tisserand-ec.com)<br>Accounting and SAP consulting firm assisting SMEs and small businesses with daily administrative, financial management, and growth strategy support. | Accounting | 🇫🇷 Tremblay-en-France | 18 |  |

## 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.

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Source: https://www.tamtam.ai/l/consulting-firms-seine-saint-denis