After completing an arts degree at University of Paris X: Nanterre, Leymergie began his career at the External Affairs and Cooperation department (now Radio France Internationale) of the Office de Radiodiffusion Télévision Française (ORTF) in 1970.

After a period at the National Audiovisual Institute (INA), Leymergie worked as a journalist in the children's programming department of Antenne 2 from 1978 to 1984, where he produced programmes such as Disney Dimanche in 1979 and Récré A2 in 1980.

His only other television activity during this period was a stint co-hosting the 13:00 Antenne 2 news with Patricia Charnelet from 1987 to 1990.

During this period, the broadcast beat the 13:00 TF1 news, read by Yves Mourousi, in the ratings, which has not happened again since.

Leymergie sang the French-language version of the theme song of the television series based on the Pac-Man arcade game, and has appeared in small roles in various movies.