Vietcombank sold the dollar at VND25,502, down 0.04% from the weekend. The greenback rose 0.2% to VND25,760 on the black market.
The State Bank of Vietnam lowered its reference rate by 0.04% to VND24,288.
Since the beginning of the year, the dollar has increased by 4.43% against the dong.
Globally, the dollar rose against the yen on Monday after Japan's top central banker flagged further policy tightening ahead but left open the question of timing, leaving the market no clearer on whether a move would come next month, Reuters reported.
The dollar edge up 0.6% to 155.09 yen and away from Friday's low of 153.86. It pulled back late last week after Japanese Finance Minister Katsunobu Kato on Friday put the market on warning of possible intervention if the yen fell too far and too fast.
That retreat had helped steady the euro for the moment at $1.0543, though that was still uncomfortably close to the recent one-year trough of $1.0496.
Against a basket of currencies the dollar held at 106.660, having touched a one-year top of 107.07 on Friday. The index climbed 1.6% over the week, marking six weeks of gains in the last seven.