In this video, learn how to remove the pee smell from a mattress. First, absorb as much of the urine as possible with a paper towel. Using a mixture of heavy-duty laundry detergent and warm water, gently scrub the spot with a brush or cloth. Let a layer of baking soda sit on the spot for several hours to remove the smell. It’s a simple cleaning process that will keep your mattress smelling like new.