Vietcombank sold the greenback at VND25,000, down 0.20% from Thursday.
The State Bank of Vietnam kept its reference rate stable at VND24,118.
The dollar jumped 0.44% to VND25,210 on the black market.
It has risen 2.29% against the dong since the beginning of the year.
Globally the dollar wobbled on Friday and looked set for a third straight month of declines as investors weighed U.S. data to gauge the pace of interest rate cuts, while China's spree of stimulus measures kept risk-sensitive currencies aloft, Reuters reported.
The dollar index, which measures the greenback against a basket of currencies including the yen and the euro, was last at 100.69, not far from the 14-month low of 100.21 it touched on Wednesday. The index is on course for fourth straight week of declines and third monthly loss in a row.