Blot away as much urine as possible with a dry towel. Continue to blot at the stain until no more urine transfers to the towel.
Saturate the stain and surrounding area with vinegar. Blot the vinegar with a clean, dry towel. Continue blotting the stain until no more vinegar transfers to the towel.
Cover the stain with a thin layer of baking soda to neutralize odor. Allow the baking soda to penetrate for 24 hours.
Vacuum the mattress to remove the baking soda. Verify that the odor is removed. Place clean bedding on the mattress and resume regular use.