Tribolium castaneum (Herbst, 1979) (Coleoptera: Tenebrionidae), commonly known as the red flour beetle, is one of the most destructive pests of stored grain products worldwide. This study aimed to identify T. castaneum populations collected from Sabah, Penang, and Selangor using both morphological and molecular approaches and to assess their genetic structure and diversity. Morphological identification confirmed all specimens as T. castaneum.