Vietcombank sold the greenback at VND26,409, up 0.004% from the weekend. The currency slid 0.16% to around VND27,456 on the black market.
The State Bank of Vietnam raised its reference rate by 0.004% to VND25,152.
Globally, the U.S. dollar edged lower on Monday ahead of a week crammed with central bank meetings and headlined by the U.S. Federal Reserve, where an interest rate cut is all but priced in but a divided committee makes for a wild card.
The dollar index was off 0.1% at 98.876, hovering near one-month lows touched on December 4.
It slipped 0.2% on the yen to 154.99, with markets increasingly confident the Bank of Japan will raise its rates at a policy meeting next week. The euro was a shade firmer at $1.1654, just short of its recent seven-week high of $1.1682.
"Core PCE data came and went without incident, which leaves the Fed on track to cut rates this week," KCM Trade Chief Market Analyst Tim Waterer told Reuters. "The anticipated rate cut this week is keeping the dollar in check while simultaneously giving the gold price some room to move northwards."