The JS9 was designed by Gérard Ducarouge and Michel Beaujon, with Robert Choulet working on aerodynamics.

[3] For the 1978 season, Ligier continued to run a single entry for Jacques Laffite, the team's regular driver.

[1] After completing the first six races of the season with the JS7 and JS7/9 (a hybrid car),[3] the JS9 made its debut at the Monaco Grand Prix.

At the next race in which the JS9 ran, the Spanish Grand Prix, he finished on the podium in third, having qualified tenth.

Laffite enjoyed good reliability, retiring from just two races, Monaco and the season ending Canadian Grand Prix.