To remove urine stains from a mattress, you will need: 1  Laundry detergent. 2  Vinegar. 3  Baking soda. 4  A vacuum. 5  To remove urine stains from a mattress, you need to first blot up as much of the urine as you can when it first happens. Rub the soapy solution onto the urine stain on the mattress. 2  Using a sponge, scrub the soap on the urine stain. 3  Continue to do this until the stain fades. 4  Once it has faded, allow the mattress to dry. 5  If the detergent fails to remove the urine stain from your mattress, try using vinegar and baking soda.