A cotton cultivar, designated PM 3225 B2RF, is disclosed. The invention relates to the seeds of cotton cultivar PM 3225 B2RF, to the plants of cotton PM 3225 B2RF and to methods for producing a cotton plant produced by crossing the cultivar PM 3225 B2RF with itself or another cotton variety. The invention further relates to hybrid cotton seeds and plants produced by crossing the cultivar PM 3225 B2RF with another cotton cultivar.