Vietcombank sold the greenback at VND24,800, up 0.20% from Wednesday.
The State Bank of Vietnam lowered its reference rate by 0.12% to VND24,105.
The dollar rose 0.12% to VND25,100 on the black market. It has risen against the dong by 1.47% this year.
Globally the dollar held firm on Thursday following its sharpest rally since early June as traders looked ahead to speeches from key Federal Reserve policy makers later in the day for clues on the pace of interest rate cuts, Reuters reported.
The U.S. currency rebounded strongly overnight from a more than one-year low to the euro and 2 1/2-year trough versus sterling.