Christopher Nkunku began playing football with AS Marolles as a six-year-old. In 2009, he joined Fontainebleau, where he was spotted by scouts of several professional clubs.
Due to being considered too young and light, Nkunku was not signed by Lens, Le Havre and Monaco; clubs where he had been on trials. He eventually signed with Paris Saint-Germain. He made 78 appearances for them and won three Ligue 1 titles, the Coupe de France twice and the Coupe de la Ligue twice.
Nkunku then joined German side RB Leipzig in July 2019, with whom he won the Bundesliga Player of the Season award and the DFB-Pokal in the 2021–22 season after scoring 20 times and assisting 13 goals in 34 league games.