PSG countersued Mbappe, who moved to Real Madrid last year, for 180 million euros in Paris' labour court, basing that figure on a botched 300 million-euro transfer to Saudi club Al-Hilal, which the player refused.
Mbappe, 26, initially filed a complaint in June over the way he was treated by PSG at the start of the 2023/24 season.
He believes he was sidelined by the Qatari-owned club and made to train with players the club were trying to offload after refusing to agree a new contract.
It is a practice which has also affected other footballers and prompted the French players' union to complain last year.
Mbappe was not invited to take part in PSG's 2023 pre-season tour of Asia and missed the first game of that season, but was later restored to the team after holding talks with the club.
After seven seasons with PSG, he joined Real Madrid on a free transfer last summer, where he earns a reported annual salary of 30 million euros.
He scored 256 goals in 308 games for PSG, but the club won the Champions League for the first time last season following the striker's departure.