PSG lost 3-2 to Madrid in the Champions League, and reports claimed Neymar and Donnarumma had to be pulled apart in the dressing room after Wednesday's defeat.
The report claimed the pair clashed and blamed each other for the loss. However, both players denied the report, with Neymar taking to Instagram to address the matter.
"I hate coming here and talking about news, but the previous post is a lie," Neymar said on Instagram. "There was no fight inside the locker room.
"Incompetent journalists who want to promote themselves, try the next one ok?"
Neymar also posted a screenshot of a private WhatsApp conversation with Donnarumma, with Donnarumma saying: "Sorry about yesterday. This information is unacceptable."
To which Neymar replied: "My friend! Don't worry, it can happen in football. We're a team and we're with you. You're very young and you will win a lot of titles. Get up and let's move on! Friendship."
Marca alleged Neymar was frustrated with Donnarumma's criticism of the Brazilian. The goalkeeper reportedly "did not shut up" and "reminded" the winger for losing the ball for Madrid's second goal on the night.
PSG currently sit on top of Ligue 1, with Nice second, trailing Mauricio Pochettino's side by 13 points.