In 1772, after apprenticeships under a topographical draughtsman and an enamellist, Grandjean entered the studio of Jurriaan Andriessen in Amsterdam. Andriessen's studio specialised in painting wall decorations and it was here that the artist was trained in landscape and figure painting. It was after he left this studio and with the help of several wealthy patrons that he decided to visit Italy to further his artistic skills. On 2 June 1779 he sailed for Rome. On arrival in Italy his artistic style rapidly transformed from traditional draughtsmanship to a more mature neo-Classicism, and this was reflected in the 60 or 70 landscape and figure studies that he sent back to his native Holland.
Grandjean died in Rome of influenza, barely two years after his arrival in Italy.