Yes, mold can grow inside of a mattress. Foam mattresses with open-air chambers are especially prone to developing mold if used in a humid or moist environment. If sleepers become too hot and begin to sweat, they may unintentionally create a mold-friendly environment in their mattress. The best way to prevent mold from growing inside of a mattress is to keep it covered with a water-repellent, hypoallergenic protective covering at all times. Not only will doing so prevent mold, but it will also keep bed bugs and pests from invading your bed, prevent bad smells from clinging to your mattress, and ensure that spills never stain the fabric of the mattress. Those who suspect that their mattress contains mold could choose to have it cleaned and sterilized by a professional. However, you might want to replace the mattress instead of spending the money required for a professional cleaning.