Phan Thanh Duoc, 42, was held by police in Tan Chau Town for violations when piloting waterway vessels.
On April 19 he was helming Hang Chau Tourist Express Boat, which was carrying 42 tourists from Phnom Penh in Cambodia to Chau Doc, when it was hit by the ferry on the Tien River in An Giang Province.
A 36-year-old tour guide was killed, and a Frenchman and a German were injured.
Authorities said Duoc did not control the speed and distance from the other vessel, leading to the collision.
Hoang Thi Minh Dang, the company that organizes tours using the vessel, had said Saturday Duoc has all the necessary qualifications for the job and over 10 years' experience.
Nguyen Khanh Hiep, director of the An Giang Province Department of Culture, Sports and Tourism, said there would be an assessment of Hang Chau's operations, and any possible violations would be penalized.