Vietcombank sold the dollar at VND24,840, up 0.28% from Tuesday.
At unofficial exchange points, the greenback slid 0.2% to VND24,950.
The State Bank of Vietnam raised its reference rate by 0.04% to VND24,151.
The dollar has risen against the dong by 1.72% since the beginning of the year.
Globally, the dollar wavered on Wednesday, while the yen regained some lost ground as investors made last-minute tweaks to positions ahead of a policy meeting expected to begin a U.S. easing cycle, Reuters reported.
The dollar has fallen along with U.S. yields since July and at $1.1125 per euro is not far from the year's low at $1.1201 in anticipation of U.S. easing at a clip, with more than 100 basis points of rate cuts priced in by Christmas.
The yen, up more than 12% since July, has been surging because the Bank of Japan - which sets policy on Friday - has been hiking rates at the same time as the Fed prepares to cut.
It rose about 0.7% to 141.41 per dollar on Wednesday, recouping part of an overnight drop. The yen was up 0.6% to 157.37 per euro.