Barton, who completed a season-long loan switch to the French club last month, has grabbed the headlines on numerous occasions back in England due to his antics on and off the pitch.
"He is truly a nice person," Ayew told Marseille's official website.
"It's maybe the case that, on the pitch, he is different, with another kind of desire, another kind of commitment, another kind of aggression. But away from it he's truly a good person."
Barton recently announced that he would be temporarily leaving Twitter to concentrate on football matters with Marseille.