The sale of 124.7 million shares was done between July 21 and August 9, according to a company disclosure.
Tuan earned an estimated VND2.6 trillion from it.
Funderra, a company affiliated with his father Dang Khac Vy, bought the same number of shares that Tuan sold.
VIB closed last week at VND20,550 representing a nearly 40% gain since the beginning of the year, giving the bank market capitalization of VND52 trillion.