Lemonnier studied under Descamps and Vien. He won the Grand Prix de Rome in 1772 with The Children of Niobe Killed by Apollo and Diana (Rouen, Museé des Beaux-Arts). Lemonnier became an Academician in 1789 and exhibited historical and mythological subjects at the Salon from 1785-1814. He was administrator of the Gobelins Factory between 1810 and 1816.