The incident happened took place in Uttar Pradesh's Baghpat on Sunday.
As per reports, the baby Keshav Kumar, was sleeping next to his grandmother in a room on the terrace and the door was left open.
The monkeys at one point entered the room and dragged away the baby.
Upon not finding the baby beside her, the grandmother raised an alarm and the family began searching for the toddler.
Unfortunately, he was later found floating in the water tank.
According to the baby's parents, the monkeys had tried to take away their baby earlier also but were unsuccessful.
"The monkey menace is a major issue and we are informing forest officials to take necessary action," O.P. Singh, Station House officer (SHO) Chandinagar, said.