Vietcombank sold the dollar at VND24,750 Monday, down 0.06% from Sunday.
The State Bank of Vietnam's reference rate remained unchanged for the fourth day at VND24,036.
The greenback went up 0.10% to VND25,060 on the black market.
It has increased by 1.35% against the dong since the beginning of the year.
The dollar started the week on a steady footing as investors took stock of U.S. economic data ahead of the Federal Reserve policy meeting this week, while escalating geopolitical tensions in the Middle East kept risk sentiment in check, Reuters reported.
The dollar index, which measures the U.S. currency against six rivals, inched 0.01% higher to 103.55 on Monday, set for a 2% gain in January as traders temper expectations of early and deep U.S. interest rate cuts.
The euro was down 0.05% at $1.0847, while Sterling was last at $1.2703, up 0.04% on the day ahead of Bank of England meeting later this week. The Japanese yen strengthened 0.01% to 148.14 per dollar on Monday.
The Asian currency is down nearly 5% against the dollar in January, on course for its weakest monthly performance since June 2022.