Blot up any fresh urine with clean paper towels or a dry cloth
Strip off all bedding and wash it separately
Mix equal parts white vinegar and water in a spray bottle
Lightly spray the stained area until damp, not soaked
Blot again with clean towels
Sprinkle a generous layer of baking soda over the area
Let the baking soda sit for several hours or overnight
Vacuum up the baking soda completely
Repeat the vinegar and baking soda treatment if needed
Use an enzyme cleaner made for pet or urine odors if the smell remains
Allow the mattress to air dry fully in a well-ventilated room
Place the mattress in sunlight if possible
Use a fan to speed up drying
Avoid using heat until the odor is gone
Use a waterproof mattress protector after cleaning
Replace the mattress if the smell has soaked deeply and will not come out