The invention relates to the novel cotton variety designated 12R224B2R2. Provided by the invention are the seeds, plants, plant parts and derivatives of the cotton variety 12R224B2R2. Also provided by the invention are methods of using cotton variety 12R224B2R2 and products derived therefrom. Still further provided by the invention are methods for producing cotton plants by crossing the cotton variety 12R224B2R2 with itself or another cotton variety and plants and seeds produced by such methods.