The typhoon, bearing winds of up to 90 kilometres per hour (55 miles per hour), hit Vietnam on Tuesday afternoon after moving through the Gulf of Tonkin from China's Hainan island, but it weakened as it headed inland.
Torrential rains and heavy winds lifted roofs of houses and felled electricity pylons and tens of thousands of trees.
One fisherman was killed while dropping anchor on his boat at Do Son port near the northeastern coastal city of Haiphong, an official from the Central Committee for Flood and Storm Control said.
Another person was killed in the Tam Diep district of Ninh Binh province after being hit by a falling tree.
Eighteen people were also hurt by flying debris in the four northern coastal provinces of Thai Binh, Nam Dinh, Ninh Binh and Thanh Hoa. Power supplies in the region were cut for hours, the Thanh Nien newspaper reported.
Trees were also blown down in Hanoi, which has been under a deluge of rain since Tuesday.
Vietnam was bracing for further bad weather as Typhoon Imbudo swept out of the Philippines across the South China Sea towards Hong Kong early Wednesday.
"There is a strong possibility the typhoon will hit Vietnam but we do not know how strong it will be when it lands. It looks as though it will weaken as it nears us," the official said.
The typhoon killed at least 17 people and left more than 11,000 others displaced in the Philippines.