According to Corriere dello Sport, in a recent picture posted by Costa, Zaniolo commented: "Stop mum. What are you doing with your mouth like that? You're 40!".
It's not the first time the young prodigy's mum has left him red-faced.
Costa recently spoke of the time she embarrassed Zaniolo when the duo met club legend Francesco Totti.
"I saw him the first time we were in Trigoria. He came to us and I started crying," she said. "He told me: 'What are you crying for me?' I could not speak.