Quebec police spokesman Sgt. Marc Tessier said the girl was playing with another, older girl along the river near Ferme-Neuve on Friday when the girl slipped under the water at about 4:30 p.m. ET.
A number of families were nearby. Tessier said the older girl notified the five-year-old's parents, and a number of people raced into the water to search for her.
Emergency crews called to the scene were unable to find the girl on Friday, and a search resumed Saturday morning.
Tessier said the girl's body was found at about 8:45 a.m. ET just three metres from where she had fallen in. She had not been wearing a life jacket.
An investigation is underway.
This is the 33rd drowning in the province this year, 11 more than this time last year.
Raynald Hawkins, general director of Quebec's Lifesaving Society, said the river's fast currents may have dragged the toddler underwater.
Last weekend, a 39-year-old man from Gatineau, Que., drowned after he fell into the same river, about 40 minutes away in Notre-Dame-de-Pontmain, Que.