Vietcombank sold the dollar at VND24,760, up 0.24% from Sunday.
The State Bank of Vietnam lowered its reference rate by 0.08% to VND24,090.
The dollar went up 0.04% to VND24,640 on the black market.
It has increased against the dong by 4.34% since the beginning of the year.
Globally, Japan's yen weakened briefly on Monday to the 150-per-dollar level, as elevated U.S. Treasury yields kept the dollar supported across the board but without pushing it too much higher, Reuters reported.
Investors are waiting for several events this week, including the European Central Bank meeting, and the release of U.S. GDP data and the Federal Reserve's preferred inflation gauge.