Vietcombank sold the dollar at VND24,740, up 0.04% from the weekend.
The greenback was steady at VND25,030 at unofficial exchange points.
The State Bank of Vietnam lowered its reference rate by 0.14% to VND24,137.
The dollar has risen against the dong by 1.31% since the beginning of the year.
Globally, the yen lounged around its highest levels for the year on Monday in trading thinned by a holiday in Japan, as market participants vacillated over the expected size of the Federal Reserve's almost-certain rate cut later this week, Reuters reported.
The dollar index, a gauge of its value against six major peers, was 0.1% lower at 101. The euro was up 0.11% at $1.1088.
The dollar was flat at 140.86 yen, near where it finished last week and close to the 140.285 end-December low it struck on Friday. It fell 1.3% on the yen last week.