It dropped 0.35% to VND25,730 at unofficial exchange points.
Vietcombank maintained its rate at VND25,450.
The State Bank of Vietnam kept its reference rate stable at VND24,245.
The greenback has increased against the dong by 4.22% since the beginning of the year.
Globally the dollar retreated against major currencies on Friday as market speculation continues to swirl about the timing of Federal Reserve interest rate cuts amid signs of cooling yet persistent inflation and a softening U.S. economy, Reuters reported.
While consumer prices for April, reported on Wednesday, rose less than expected - leading to a risk-on flavor in equity markets - various Fed officials have sounded words of caution about when rates may fall, limiting the dollar's decline this week.
The dollar index, which tracks the U.S. currency against six peers, slid 0.04% to 104.44 after earlier trading about 0.3% higher.