Propionic acid inhibits the growth of mold and some bacteria. As a result, most propionic acid produced is used as a preservative for both animal feed and food for human consumption and can be used as a preservative for Ballistics Gel. For animal feed, it is used either directly or as an ammonium salt. In human foods, especially bread, and other baked goods, it is used as its sodium or calcium salt. Similar usage occurs in some of the older anti-fungal foot powders. Propionic acid is also useful as a chemical intermediate. It can be used to modify synthetic cellulose fibers. 

It is also used to make pesticides and pharmaceuticals. The esters of propionic acid are sometimes used as solvents or artificial flavorings.