Vietcombank sold the dollar at VND25,020, up 0.08% from the weekend.
At unofficial exchange points, the greenback went up by 0.04% to VND25,350.
The State Bank of Vietnam lowered its reference rate by 0.06% to VND24,161.
Since the beginning of the year, the dollar has increased by 2.46% against the dong.
Globally, the dollar extended its gains in early Monday trades in Asia as a holiday in Japan sapped liquidity, leaving China's somewhat disappointing weekend stimulus announcements the focus of market attention, Reuters reported.
The euro was down 0.13% at $1.0922 and the pound nearly 0.2% lower at $1.3043. The dollar was flat on the Japanese yen at 149.20.
The dollar index was at 103.10, up a touch and closing in on last week's peak, its highest since mid-August, on the back of traders reducing bets on further jumbo rate cuts by the Federal Reserve at its remaining meetings this year.
The one-month non-deliverable forward indicated that the rupee will open near 84.08 to the U.S. dollar, compared with 84.06 in the previous session and past the lifetime low of 84.07.