"According to our official count as of Tuesday afternoon from the local authorities, the typhoon killed 22 people," said an official with Vietnam's national flood and storm control committee.
The official said losses were heaviest in inland Kon Tum province, where nine people had died.
He added that the typhoon made landfall at about 0700 GMT about 80 kilometres (50 miles) south of Vietnam's fourth-largest city, Danang.
Ketsana killed at least 240 people and left nearly 400,000 homeless in the Philippines.
Danang as well as Hue, the former capital and a UNESCO World Heritage site were damaged.
More than 1,000 passengers were stranded at Hue's train station, said Nguyen Ngoc Thien, president of the People's Committee, or communist local government, in Thua Thien-Hue province.
"There were two dead and three injured in our province," he said, adding that 300 houses were damaged.
Authorities mobilised several thousand police and military personnel with armoured cars to help residents escape the typhoon's path, said Nguyen The Hung of the flood and storm control committee.
The agency said 168,585 people in six coastal provinces were evacuated.
They were moved to schools, military camps and newly built high-rise apartments.
Vietnam Airlines suspended flights to Hue and Danangbut but said they would resume on Wednesday, Sep 30.