Phan Quoc Huy, 30, was commended and rewarded for the act by the Cai Be District People's Committee on Saturday.
Huy, a beverage vendor, had saved the boy six days prior.
Nguyen Hong Son, deputy head of the Cai Be police, said Huy's heroic act was commendable and an example for people to follow.
Le Van Vu, 64, the grandfather of the rescued boy, said he was grateful for Huy's actions.
"Thanks to Huy, my grandson was seemingly reborn again," Vu said.
Huy, whose hometown is in Thua Thien-Hue in central Vietnam, came to Saigon five years ago to sell beverages and offer bodybuilding services. Two months ago, he and his wife decided to go to Tien Giang and open a beverage stall in front of their house.
On Sunday last week, which was the second day of the Lunar New Year, while his wife was delivering drinks to their customers, Huy saw a boy struggling in a canal near his home. He first thought the boy was learning how to swim, but there were no adults around, so he called for help and jumped into the canal to save the boy.
Authorities said Le Huynh Hai, 25, threw the boy into the canal after using drugs and fled the scene of the crime. He has since been apprehended for attempted murder.
The boy had floated for 30 meters before he was rescued. After spending five days at the hospital, he has been discharged.