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List of professional services firms in the Loire-Atlantique department

Tamtam tracks 158 professional services firms headquartered in the Loire-Atlantique department. This list ranks the 30 largest by number of employees on LinkedIn, led by Experis France, 𝗚𝗘𝗢𝗙𝗜𝗧 and MCI SAS. Their median headcount is 385. Half of them were founded in 1999 or later. The most common headquarters are Nantes (13), Saint-Herblain (9) and Carquefou (2).

🇫🇷 Loire-Atlantique30 companiesUpdated Nov 13, 2026

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.

#CompanyIndustryHeadquarters EmployeesFounded
1
Experis Franceexperisfrance.fr

Supports DSI with innovative digital transformation projects, providing IT services and talent solutions to enhance organizational performance, addressing specific needs.

IT Services and IT Consulting 🇫🇷 Nantes 2,207 n/a
2
𝗚𝗘𝗢𝗙𝗜𝗧geofit.fr

Designing geographical databases, securing land processes for private and development projects, producing national cartography, developing agriculture, and managing natural resources.

Space Research and Technology 🇫🇷 Nantes 1,157 1968
3
MCI SASmci.fr

This company specializes in commercial and industrial refrigeration, climate engineering, and energy performance optimization for installations across various sectors.

HVAC and Refrigeration Equipment Manufacturing 🇫🇷 Carquefou 1,106 1963
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.

IT Services and IT Consulting 🇫🇷 Saint-Herblain 797 1999
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

Environmental Services 🇫🇷 Nantes 625 1982
6
Bessébesse.fr

An independent insurance brokerage company with over 60 years of experience, specializing in protecting businesses and employees with innovative solutions and quality services

Insurance 🇫🇷 Nantes 610 1960
7
ASI ®asi.fr

Working towards a responsible digital world dedicated to serving humanity

IT Services and IT Consulting 🇫🇷 Saint-Herblain 590 1993
8
Consertoconserto.pro

Offers IT consulting and expertise services across cloud, digital, and embedded domains through consulting, delivery centers, and labs models.

IT Services and IT Consulting 🇫🇷 Saint-Herblain 555 2013
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

Human Resources Services 🇫🇷 Saint-Herblain 549 1991
10
IMATECHima.eu

Development and integration of advanced technology solutions, software services, and digital transformation support for various industries and businesses.

Information Services 🇫🇷 Nantes 534 1999
11
DeCA Propretédeca-proprete.fr

Provides tailored cleaning and maintenance services to professional clients, ensuring high-quality results with advanced techniques and equipment.

Environmental Services 🇫🇷 Treillières 501 1996
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.

Engineering Services 🇫🇷 Nantes 501 1978
13
4CAD Group4cadgroup.com

The company offers PLM, ERP, and IoT tools to help organizations optimize their information systems for increased industrial efficiency

Software Development 🇫🇷 Bouguenais 463 2004
14
Edeisedeis.com

Specializing in engineering, operation, and construction solutions for the future, this company aims to become a leader in construction services and technical management

Engineering Services 🇫🇷 Nantes 412 2016
15
Atlantic Ingénierieatlantic-ingenierie.com

Engineering firm specializing in energy and telecommunication network deployment, providing expert studies and support for projects of all sizes.

Business Consulting and Services 🇫🇷 Saint-Herblain 385 2001

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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

Construction 🇫🇷 Nantes 318 2004
17
AISgroupeais.fr

AIS is a human-centric company providing expertise to clients since 1985, focusing on professional growth and fulfillment of its employees

IT Services and IT Consulting 🇫🇷 Saint-Herblain 289 1985
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.

Engineering Services 🇫🇷 Saint-Herblain 230 1958
19
Younupyounup.fr

This company offers IT services, supporting clients throughout the software lifecycle from requirements to production, focusing on web, DevOps, data, AI, agility, mobile, and cloud.

IT Services and IT Consulting 🇫🇷 Nantes 224 2019
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

Human Resources Services 🇫🇷 Nantes 203 2021
21
COCERTOcocerto.fr

Provides comprehensive accounting, audit, payroll, legal support, and digital tools to optimize and secure business operations with personalized service.

Accounting 🇫🇷 Nantes 200 1971
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

Business Consulting and Services 🇫🇷 Nantes 194 2006
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

IT Services and IT Consulting 🇫🇷 Saint-Herblain 190 1999
24
Compaslecompas.fr

Specializing in social observation of territories, creating observatories, conducting studies, and providing training for local governments to address social realities effectively

Research Services 🇫🇷 Nantes 182 1996
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.

Business Consulting and Services 🇫🇷 La Chapelle-sur-Erdre 177 1958
26
SAPRENAsaprena.com

Creation of sustainable jobs for people with invisible disabilities in sectors like cleaning, landscaping, logistics, industrial maintenance, catering, and packaging.

Business Consulting and Services 🇫🇷 Bouaye 169 1987
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

Business Consulting and Services 🇫🇷 Chateaubriant 166 2008
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.

Retail Office Equipment 🇫🇷 Saint-Sébastien-sur-Loire 164 2000
29
MOCAasi.fr

MOCA by ASI specializes in offering technical expertise and support for Microsoft solutions to users within the Microsoft ecosystem

IT Services and IT Consulting 🇫🇷 Saint-Herblain 159 2022
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

IT Services and IT Consulting 🇫🇷 Carquefou 150 1999

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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.

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