In a tweet, the Twitch star said she had "passed away peacefully this morning".
"She was an angel on earth and I couldn’t have been a more blessed grandchild to have had her in my life," he wrote.
The news was greeted with messages of condolences from many of gaming's biggest personalities including Jack "CouRage" Dunlop, Nick "NICKMERCS" Kolcheff, and Imane "Pokimane" Anys.
Ninja, who is arguably the most recognisable gamer on the planet and has deals with Red Bull, Adidas, and his own Fortnite skin, also revealed that was taking, if not a break, a step back until after the funeral.
He said: "The funeral is next week, I won’t really be super active until after. Love you all."
Feature image courtesy of Red Bull.