It is used primarily to control mold, blight, and other fungally caused diseases in fruits (e.g. oranges) and vegetables; it is also used as a prophylactic treatment for Dutch elm disease.
Use in treatment of aspergillosis has been reported.
As an antiparasitic, it is able to control roundworms (such as those causing strongyloidiasis), hookworms, and other helminth species which attack wild animals, livestock and humans. 
Medicinally, thiabendazole is also a chelating agent, which means that it is used medicinally to bind metals in cases of metal poisoning, such as lead, mercury or antimony poisoning.
In dogs and cats, thiabendazole is used to treat ear infections.
Thiabendazole is also used as a food additive, a preservative with E number E233 (INS number 233). For example, it is applied to bananas to ensure freshness, and is a common ingredient in the waxes applied to the skins of citrus fruits. It is not approved for usage in the EU, Australia and New Zealand or the USA.