Vietcombank sold the greenback at VND25,460, down 0.02% from Monday.
The State Bank of Vietnam lowered its reference rate by 0.02% to VND24,248.
On the black market, the dollar was sold at VND25,880, up 0.35%.
It has gained 4.15% against the dong since the beginning of the year.
Globally the dollar softened as traders squared positions on the day of the U.S. presidential election, after recent polls dented some market bets on a victory for Republican Donald Trump, Reuters reported.
Overnight, the U.S. currency slumped as much as 0.76% against the euro to a three-week trough after a weekend opinion poll showed Harris with a surprise lead in Iowa, a traditional Republican stronghold. Overall, polls continue to show a tight race.
The dollar index, which measures the currency against six major peers including the euro, edged down slightly to 103.89, after slumping as low as 103.67 on Monday for the first time since Oct. 21. Last week it surged to the highest since the end of July at 104.63.