Following PSG's 6-1 defeat in the second leg of the knockout rounds, the politician has held up his side of the bargain.
Back in spring, when the Paris football team won against Barca 4-0, Charles Dayot said: "If Barca qualifies, I'll eat a rat and I'll vote for [left-wing presidential candidate Jean-Luc] Melenchon."
Dayot, who was elected mayor of Mont-de-Marsan in south-west France earlier in July, admitted he hadn't carried out the second promise, but followed through on his vow to eat a rodent, according to French radio station RTL.
The meal took place on Saturday, during the Fetes de la Madeleine, a local festival. Dayot tucked into a coypu, a large semiaquatic rodent cooked up by local chefs - and the table was decorated with a Barca football shirt, while he used his Paris shirt as a napkin.
"I'm never making a bet again."
Video: Sud Ouest France
Dayot said the rodent was "very well cooked" and tasted "a little bit like rabbit" in video footage shared on social media.
He later rounded off the festival by challenging the mayor of nearby Saint-Sever to a donkey race, which resulted in a draw.