Vietcombank sold the dollar at VND25,070, down 0.32% from the weekend.
The greenback was stable at VND25,300 at unofficial exchange points.
The State Bank of Vietnam raised its reference rate by 0.017% to VND24,254.
The dollar has risen against the dong by 2.66% since the beginning of the year.
Globally, the yen rose to a three-week high against the dollar on Monday as Federal Reserve Chair Jerome Powell's emphatic dovish shift contrasted sharply with Bank of Japan chief Kazuo Ueda's steadfastly hawkish tone, Reuters reported.
The dollar index - which measures the currency against a basket of six major peers, including the euro, sterling and yen - languished at 100.64, just off the 13-month low of 100.60 reached at the end of last week.
The U.S. currency hovered near its lowest in 13 months against the euro. It also sagged closer to levels last seen in March 2022 versus sterling.
The euro was little changed at $1.1190, not far from its Friday high of $1.1201, a level last seen in July of last year.
The dollar sank as much 0.59% to 143.56 yen for the first time since Aug. 5 in the early hours of Monday before last trading down 0.25%.
Sterling was steady at $1.3215 after jumping as high as $1.32295 on Friday for the first time in 17 months.