He was tracked by the location of his mobile phone and was rescued from Mumbai's Churchgate area last night, Karni Vihar police station SHO Mahaveer Singh said.
"A knife was also recovered from his possession. He said he was in the last stage of the game and might have committed suicide," Mr Singh said, adding, the boy was handed over to his family members.
The 'Blue Whale Challenge' is an online game, blamed for over 100 child suicides across the world. It has provoked a huge concern in India amid reports that more than six deaths over the past few weeks are linked to it.