Tanguy Cotte-Martinon joined SNCF in 1997, after studying at the Institut National des Sciences Appliquées in Lyon and Washington University in Saint Louis. He held several positions until 2005, including responsibility for the overhaul of freight production in the Hauts-de-France region and project management for the T11 tram-train line in the Ile-de-France region.

As Chief of Staff to the Chairman of SNCF from 2005 to 2008, he worked successively with Louis Gallois, Anne-Marie Idrac and Guillaume Pépy.

From 2008 to 2013, he was Director of Operations and Traction at Paris Nord, responsible for a number of projects to improve the operational and service performance of the mass-transit business.

From 2013 to 2015, in Brussels, he transformed Thalys into a fully-fledged rail company, enabling the development of cross-border high-speed services in Northern Europe. For more than two years, as Director of Onboard and Station Services, he then helped SNCF Voyageurs transform the jobs of its 16,000 on-board and station staff to improve the customer experience. From 2018 to 2020, he was in charge of the TGV Nord Business Unit and led a major transformation of the high-speed offer to strengthen the customer experience and the competitiveness of the service.

Since 2020, Tanguy Cotte-Martinon has held the position of Director of Finance, Strategy and Legal for the TGV-Intercités business and managed the subsidiary holding SNCF Voyageurs interests in its European rail companies.