The lawyers said several of the club's accounts had been frozen on Thursday.
"We're going to go on the attack," Delphine Verheyden, Mbappe's lawyer, told a press conference.
The French League (LFP) ordered PSG to pay the player last year but the French Football Federation ruled that Mbappe's request was inadmissible because of an ongoing procedure in a civil court.
Mbappe's legal team, however, have turned to a Paris court to freeze 55 million euros in PSG's accounts.
"We have protectively seized the accounts of PSG, to the tune of 55 million euros, this morning," Thomas Clay, one of Mbappe's legal experts, said.
PSG said in October that they would be "forced to bring the case before the competent courts" while they were still trying to find an "amicable solution" with Mbappe.
"After hearing yet another fantastic story from a parallel universe today, PSG continues to fail to understand why Kylian Mbappe is not taking his case to the labour chamber, which is the only court competent to settle the dispute between him and his former club," PSG said on Thursday.
"His lawyers claim it's because he's not an employee like the others. PSG believes, on the contrary, that he is an employee like any other, and that he must respect the clear and repeated public and private commitments he has made to his employer.
"All the procedures announced by Kylian Mbappe's lawyers only serve to delay the resolution of the dispute by the labour chamber, before which PSG is ready to present all the facts, evidence and testimony proving the existence of an agreement, or better still by means of the transaction that PSG has been calling for over a year."
