It increased by 0.24% from Tuesday to VND25,360 on the black market.
Vietcombank sold the dollar at VND25,025, the same rate as the previous day.
The State Bank of Vietnam's reference rate was stable at VND24,168.
The greenback has increased by 2.39% against the dong since the beginning of the year.
Globally, the dollar drifted sideways on Wednesday, giving some relief to the yen and other major currencies after a sharp rally to a seven-week high last week, as investors paused to assess the interest rate outlook for the U.S., Reuters reported.
The dollar index, which measures the greenback against a basket of currencies, edged up 0.11% to 102.6, not far from Friday's seven-week high of 102.69.
The New Zealand dollar slumped to its lowest since Aug. 19 at $0.60705, after the Reserve Bank of New Zealand cut interest rates by 50 basis points and left the door open to yet more aggressive monetary easing.
The euro was down 0.14% at $1.0965, while the pound slid 0.15% to $1.3083, close to the more than three-week low of $1.30595 it touched on Monday.
Dollar/yen traded in a narrow range, last hovering around 148.35 yen, after touching a seven-week high of 149.10 on Monday. The Indian rupee was flat at 83.9450 against the dollar.