It depends on the specific waterproof mattress protector you have. All of the protectors we carry can be.
It's important to follow the care instructions provided by the manufacturer to ensure that the protector is washed and dried properly. Some protectors may need to be washed in cold water and tumble dried on a low heat setting, while others may be able to be washed in hot water and dried on a high heat setting. It's also a good idea to avoid using bleach or fabric softeners when washing the protector, as these can potentially damage the waterproof barrier.