The floor, set by the Vietnam Food Association, will come into effect on Jan. 12, according to a statement from the association to traders seen by Reuters on Friday.
The previous floor for the grade was set at $380 a tonne in late November.
The agriculture ministry said last month that Vietnam's rice exports in 2014 were expected to have dipped slightly to an estimated 6.53 million tonnes, putting the Southeast Asian country far behind top exporters Thailand and India.