Vietcombank sold the greenback at VND25,670, down 0.04% from the weekend. On the black market, the currency rose 0.08% to VND25,770.
The State Bank of Vietnam raised its reference rate by 0.03% to VND24,646.
Globally, the euro jumped to a one-month high and stock futures charged ahead on Monday after Germany's conservatives won the national election as expected, Reuters reported.
The euro touched a one-month top of $1.05245 in the Asian session, helped in part by a weaker dollar.
The dollar index dropped to 106.16 - the lowest since mid-December, with losses on the euro, sterling and Swiss franc.
Asian currencies were mostly higher. The dollar was pinned at 149.36 yen, having shed 2% last week to threaten chart support at 148.65.