Fresh mushrooms last about one week in the refrigerator. It is best to store the mushrooms in their original container until the package is opened.
Once the package of mushrooms is opened, store them in the refrigerator by putting the whole, unwashed mushrooms in a brown paper bag. Fold the top of the bag over to close it. Store the bag of mushrooms in the main compartment of the refrigerator. The dry paper bag absorbs any extra moisture from the mushrooms, which prevents them from getting soggy or moldy in the refrigerator. Wrapping the mushrooms in a dry paper towel can also preserve them in the refrigerator, whether they are in the original packaging or in a perforated plastic bag that allows for some air flow.