Vietcombank sold the dollar at VND24,740, down 0.08% from the weekend.
The greenback slid 0.12% to VND25,300 at unofficial exchange points.
The State Bank of Vietnam lowered its reference rate by 0.1% to VND24,093.
The dollar has risen 1.31% against the dong since the beginning of the year.
Globally, the dollar index, which measures the greenback against a basket of currencies, was flat at 100.41 on Monday after easing 0.3% last week, Reuters reported.
The euro stood at $1.1167, having bounced on Friday in the wake of the benign U.S. inflation report.