The professional services firms in Loire-Atlantique are primarily mid-sized companies, with headcounts ranging from 385 to over 2,200 employees. Many operate in IT services, consulting, and environmental services. For example, Experis France supports digital transformation projects, while Catamania provides IT consulting and software publishing. Sce Aménagement & Environnement offers urban planning and civil engineering, and DeCA Propreté specializes in cleaning and maintenance services. Bessé is an independent insurance brokerage. The FÉTIS Group provides engineering products and services for various industries, with a focus on decarbonization.
A notable pattern is the concentration of these companies in Nantes and Saint-Herblain, indicating a regional hub for professional services. The founding dates span several decades, from GEOFIT in 1968 to Edeis in 2016, suggesting a mix of established firms and more recently founded companies.
| # | Company | Employees | |||
|---|---|---|---|---|---|
| 1 |
Experis Franceexperisfrance.fr
Supports DSI with innovative digital transformation projects, providing IT services and talent solutions to enhance organizational performance, addressing specific needs. |
2,207 | |||
| 2 | 1,157 | ||||
| 3 | 1,106 | ||||
| 4 |
Catamaniacatamania.com
Provides digital transformation services, consulting, software publishing, and information system architecture for banking, insurance, and retail sectors across international agencies using diverse technical expertise. |
797 | |||
| 5 |
Sce Aménagement & Environnementsce.fr
Sustainable development firm offering urban planning, civil engineering, and environmental services globally with 45+ years of experience and 500 professionals |
625 | |||
| 6 | 610 | ||||
| 7 | 590 | ||||
| 8 |
Consertoconserto.pro
Offers IT consulting and expertise services across cloud, digital, and embedded domains through consulting, delivery centers, and labs models. |
555 | |||
| 9 |
Abalone Franceabalone-interim.com
Specialized in HR services, temporary work, recruitment, and training since 1991, this company focuses on satisfying client needs and increasing employee employability |
549 | |||
| 10 | 534 | ||||
| 11 |
DeCA Propretédeca-proprete.fr
Provides tailored cleaning and maintenance services to professional clients, ensuring high-quality results with advanced techniques and equipment. |
501 | |||
| 12 |
FÉTIS Groupfetis.group
Provides engineering products and services for off-road machinery, specialized vehicles, power generation, marine power, and manufacturing industries with focus on decarbonization. |
501 | |||
| 13 |
4CAD Group4cadgroup.com
The company offers PLM, ERP, and IoT tools to help organizations optimize their information systems for increased industrial efficiency |
463 | |||
| 14 | 412 | ||||
| 15 |
Atlantic Ingénierieatlantic-ingenierie.com
Engineering firm specializing in energy and telecommunication network deployment, providing expert studies and support for projects of all sizes. |
385 | |||
Want more companies than this list?This page shows the largest ones only. Connect to Tamtam to see every company that matches, filter by size, industry or growth, and reach their decision-makers. | |||||
| 16 |
ALTEREAalterea.fr
An all-trade and energy engineering company specializing in renovation, construction, and energy optimization projects across various sectors for over 10 years |
318 | |||
| 17 |
AISgroupeais.fr
AIS is a human-centric company providing expertise to clients since 1985, focusing on professional growth and fulfillment of its employees |
289 | |||
| 18 |
SOFRESID ENGINEERINGsofresid-engineering.com
Global engineering company with high value-added services in oil, gas, shipbuilding, steel, and construction industries. Offers turnkey projects, studies, procurement, and supervision. |
230 | |||
| 19 | 224 | ||||
| 20 |
Slash Intérim
Slash Intérim is a national network of temporary recruitment agents, aiming to blend human touch with digital innovation and empower independent recruitment professionals |
203 | |||
| 21 |
COCERTOcocerto.fr
Provides comprehensive accounting, audit, payroll, legal support, and digital tools to optimize and secure business operations with personalized service. |
200 | |||
| 22 |
MECAcluster-meca.fr
A cluster of companies offering mechanical analysis expertise to ensure safety and feasibility of constructions through material behavior, design, and stress calculation |
194 | |||
| 23 |
GROUPE SYDsyd.fr
Specializing in digital transformation, the company offers consultancy, project management, infrastructure services, Microsoft solutions integration, application development, and Microsoft expertise, emphasizing customer satisfaction and trust |
190 | |||
| 24 |
Compaslecompas.fr
Specializing in social observation of territories, creating observatories, conducting studies, and providing training for local governments to address social realities effectively |
182 | |||
| 25 |
Cerfrance Loire-Atlantiqueloire-atlantique.cerfrance.fr
Provide accounting, strategic, fiscal, legal, social, HR, and IT consulting to support local entrepreneurs and business leaders' overall performance. |
177 | |||
| 26 |
SAPRENAsaprena.com
Creation of sustainable jobs for people with invisible disabilities in sectors like cleaning, landscaping, logistics, industrial maintenance, catering, and packaging. |
169 | |||
| 27 |
ORINOXorinox.com
Software consulting and plant design firm specializing in digitalization using AVEVA software suite for engineering, asset data visualization, resources management, simulation, and training |
166 | |||
| 28 |
VFLIT - Vous faciliter l'ITvousfaciliter-it.fr
Providing integrated cybersecurity, cloud, telecom, management applications, and safety services to enhance organizational IT and communication system performance. |
164 | |||
| 29 | 159 | ||||
| 30 |
Capaciticapaciti.com
A regional leader in cybersecurity, providing specialized services in consulting, engineering, and system infrastructure support with offices in France and international project capabilities |
150 | |||
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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 13, 2026.
More company lists in the Loire-Atlantique department
- The largest companies in the Loire-Atlantique department 2,044
- Companies with in-house R&D in the Loire-Atlantique department 207
- Retail chains in the Loire-Atlantique department 162
- Multinational companies in the Loire-Atlantique department 159
- Software Development companies in the Loire-Atlantique department 137
- SaaS companies in the Loire-Atlantique department 135
- IT services companies in the Loire-Atlantique department 130
- Manufacturers in the Loire-Atlantique department 125
- IT Services and IT Consulting companies in the Loire-Atlantique department 110
- Consulting firms in the Loire-Atlantique department 94
- Distributors and wholesalers in the Loire-Atlantique department 94
- Hardware manufacturers in the Loire-Atlantique department 86
- Business Consulting and Services companies in the Loire-Atlantique department 83
- Public sector organisations in the Loire-Atlantique department 80
- Family-owned companies in the Loire-Atlantique department 71
- Education providers in the Loire-Atlantique department 68
- Real Estate companies in the Loire-Atlantique department 67
- Financial services firms in the Loire-Atlantique department 65
- Law Practice companies in the Loire-Atlantique department 62
- Retail companies in the Loire-Atlantique department 61
- Subscription businesses in the Loire-Atlantique department 61
- Critical infrastructure operators in the Loire-Atlantique department 58
- Events Services companies in the Loire-Atlantique department 58
- Construction companies in the Loire-Atlantique department 57
The same list elsewhere in France
- Professional services firms in France 6,610
- Professional services firms in Île-de-France 3,376
- Professional services firms in Auvergne-Rhône-Alpes 711
- Professional services firms in the Hauts-de-Seine department 629
- Professional services firms in Provence-Alpes-Côte d'Azur 433
- Professional services firms in the Rhône department 400
- Professional services firms in Occitanie 399
- Professional services firms in Grand Est 317
- Professional services firms in Nouvelle-Aquitaine 308
- Professional services firms in Hauts-de-France 260
- Professional services firms in Pays de la Loire 253
- Professional services firms in the Bouches-du-Rhône department 249
- Professional services firms in the Haute-Garonne department 208
- Professional services firms in the Nord department 178
- Professional services firms in Brittany 167
- Professional services firms in the Gironde department 151
- Professional services firms in Normandy 114
- Professional services firms in the Yvelines department 108
- Professional services firms in the Ille-et-Vilaine department 94
- Professional services firms in Paris 2,241
- Professional services firms in Lyon 265
- Professional services firms in Toulouse 139
- Professional services firms in Marseille 123
- Professional services firms in Boulogne-Billancourt 102