The invention relates to the novel cotton variety designated 20R824B3TXF. Provided by the invention are the seeds, plants, plant parts and derivatives of the cotton variety 20R824B3TXF. Also provided by the invention are methods of using cotton variety 20R824B3TXF and products derived therefrom. Still further provided by the invention are methods for producing cotton plants by crossing the cotton variety 20R824B3TXF with itself or another cotton variety and plants and seeds produced by such methods.