Almost 500 boats refused to operate last Friday on Halong Bay, north-east of Hanoi. because of new safety regulations which were to take effect that day.
The bay, a Unesco World Heritage site known for its stunning limestone cliffs, is one of the country's most popular tourist attractions.
The boats’ managers appealed for time to implement the safety measures, including a requirement that boats carry global positioning systems, according to officials.
The boats resumed work on Saturday after the provincial government decided to delay implementing the new regulation until 10 September, they said.
In Vietnam's worst tourism accident, 11 foreign tourists and their guide drowned in February when a boat sank at night on Halong Bay.
The boat's captain and engineer were arrested for investigation over alleged safety violations, prompting the government to draw upnew rules.
Twenty-eight French tourists had a lucky escape in May when their boat began sinking on Halong Bay. There were no injuries.