The remains of Nguyen Thi Hoi, 60, were found around 30 m from the site of the crash, a spokesperson for the Hai Phong military headquarters said.
They are expected to be taken to Bai Chay hospital before being handed over to her family, the spokesperson added.
Search and rescue efforts ended Friday morning after all the fragments of the helicopter were retrieved.
The VN-8650 helicopter piloted by Chu Quang Minh, 59, crashed with four passengers while on a sightseeing trip over Ha Long Bay on Wednesday evening.
It lost contact 10 minutes after taking off from Tuan Chau Island, and crashed into the sea seven kilometers away.
Over 300 people took part in the rescue effort.
Other victims were Hoi's husband Ho Ta Luc, Luc's sister, and a family friend.