The accident occurred at about 9 pm as the men were fishing at the Dinh Cong drainage lake in Dinh Cong Ward.
Emergency workers search for the victims (Photo: Dang Manh).
According to a witness, one man rowed a boat towards the middle of the lake to scatter snails as bait to attract fish when the boat overturned. He tried to swim back to shore but failed.
The other man, who was fishing from the bank, jumped into the water to help but also drowned.
After receiving a report, Dinh Cong Ward police joined rescue teams and the local military command at the scene. Search crews used nets and lines to scour the area where the accident occurred.
After more than two hours of searching, rescuers recovered both bodies shortly after 11 pm.
Local authorities said the victims were aged 45 and 46 and came from Bac Ninh and Thanh Hoa provinces.
Dinh Cong Lake covers more than 22 hectares and was built to help manage drainage in Hanoi. A group currently operates a fish-stocking and paid fishing service at the lake, selling tickets for timed fishing sessions.