The third eldest son of René and Denise Mercier, Jacques Mercier was educated at St. Joseph's College. Mercier joined RTBF in September 1963 and started hosting radio shows such as Sunday music (with Stéphane Steeman) and music for breakfast. In television he hosted programmes such as Game dictionary, Infernal Week, between 1980 until 1986 and again in 1989 he provided the French language commentary for RTBF viewers in the Eurovision Song Contest.