Cannibalism, an act of killing and consuming conspecific individuals, is a common behavior among various insect taxa. This study investigated the effects of food limitation and larval health status on cannibalistic behavior in the South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), a devastating insect pest on solanaceous crops. In "no-choice" trials, where either a healthy versus weak conspecific larva was provided, T. absoluta larvae exhibited a significantly higher cannibalism rate toward weak conspecific individuals compared with healthy ones. This pattern was further confirmed in "choice" trials where T. absoluta larvae significantly preferred to consume weak larvae to healthy ones when both targets were supplied. When plant food was supplied as an alternative to a healthy or a weak conspecific larva, cannibalism was observed only when weak conspecific individuals were available, despite a significant preference for tomato leaflets. Therefore, cannibalism in T. absoluta is largely opportunistic and is significantly influenced by plant food limitation and larval health status. These findings enhance our understanding of conspecific interactions in herbivorous insects.