Jarnet was first apprenticed to Patrick Rago at Maisons-Laffitte and then to Yann Porzier at Chantilly, Oise.

Jarnet rode his first winner in February 1985 at Cagnes-sur-Mer on a horse called Danini.

1991 was to also bring him victories aboard Victoire Bleu in the Prix du Cadran and Tel Quel in the Champion Stakes.

With the departure of Cash Asmussen in 1991 Jarnet also took over the role as stable jockey which made him the rider for Sheikh Mohammed in France.

In 1995, he finished only three winners in front of Olivier Peslier, who at that stage was riding the many horses that André Fabre trained for Daniel Wildenstein.