Vietcombank sold the dollar at VND24,170, up 0.08% from Thursday.
The State Bank of Vietnam lowered its reference rate by 0.05% to VND23,942.
The dollar fell 0.33% to VND24,060 on the black market.
It has increased over the dong by 1.85% since the beginning of the year.
Globally the U.S. dollar sat at an over two-month peak on Friday, on course for its sixth straight week of gains as markets await a speech from Federal Reserve Chair Jerome Powell to gauge the path of monetary policy, Reuters reported.
The dollar index, which measures the U.S. currency against six rivals, rose 0.019% to 104.11, the highest since June 7. The index is up 2% in August and set to snap its two-month losing streak.
"Market expects Powell to use the platform tonight to reiterate the ‘higher for longer’ rhetoric given how the U.S. economy has displayed relative resilience," said Christopher Wong, a currency strategist at OCBC in Singapore.