The boy went missing around 6pm yesterday as he was playing with friends around the base of the Whakatane Bridge.
He was standing on a concrete step and was seen to fall backwards approximately 1m into the water and didn't resurface.
Constable Colin Fraser from the Rotorua police Search and Rescue said they were confident they would find the boy quickly.
He went missing on high tide and due to a lack of current police believe he will be found close to the spot where he fell in. The boy's name is expected to be released as soon as he is found.
Members of the boy's family gathered at the Whakatane Rowing Club, on the banks of the river, last night.
Friends contacted the police and a search and rescue operation was immediately initiated.
Coastguard took to the water and LandSAR personnel searched the shoreline.
The Harbourmaster also provided assistance. A search was stood down around 10pm last night and resumed this morning.