Mbappe confirmed in a video posted on social media on Friday that he would be leaving PSG when his contract expires at the end of the season, ending a seven-year association with the club.
Real Madrid is expected to be the next destination for a player whose departure from Paris had been an open secret since February when he privately informed the club of his intention to move on.
Mbappe wore the captain's armband and opened the scoring early on against Toulouse to take his tally for the season to 44 goals in all competitions.
However, Thijs Dallinga quickly equalised for the visitors against a PSG side which showed 10 changes to the team knocked out of the Champions League by Borussia Dortmund in the semi-finals in midweek, with Mbappe the only player to keep his place.
Yann Gboho put Toulouse ahead with a brilliant strike in the second half, and Frank Magri wrapped up the win in stoppage time as PSG suffered just their second Ligue 1 loss this season, and their first in 27 games since September.
Mbappe has now scored 256 times for PSG, a club-record tally, since signing from Monaco in 2017 in a deal worth 180 million euros.
His tally of 191 goals in France's top flight - including 16 with Monaco at the beginning of his career - puts him in seventh place in the all-time list. Coach Luis Enrique described him as "a club legend" when he spoke to media on the eve of the game.
Jeers
PSG had indicated that celebrations after Sunday's match would be dedicated to their title triumph, rather than any specific tribute to Mbappe himself.
There were even some jeers from the crowd for the striker when the teams were read out before the game, although a huge display was unfurled before kick-off at one end of the stadium depicting Mbappe in a trademark pose with his arms folded.
The Qatar-owned club had already wrapped up a record-extending 12th French title, and 10th in the last 12 years, before hosting a Toulouse side who were themselves safe from any lingering threat of relegation.
PSG's Champions League disappointment means Mbappe will leave the club without ever having got his hands on European football's greatest prize.
With Mbappe, PSG were runners-up in 2020 and have since reached the last four on two further occasions, but the France captain will now hope to finally get his hands on the trophy at his next club.
PSG can still finish the season by completing a clean sweep of domestic honours, as they face Lyon in the French Cup final in Lyon on May 25th.
As well as Ligue 1, they have also already won the Champions Trophy, France's equivalent of a Super Cup.
Luis Enrique's team will complete their league campaign with a visit to Nice on Wednesday before going to Metz on the final day of the season next Sunday.