Larvae of Galleria mellonella are well known for their parasitisation of honeybees, so developing new methods of controlling the pest population is an important issue. The present research examined the immunotoxic effects of 2-octenoic acid against wax moth larvae. The last instar larvae were used for all experimental analyses. The tested fatty acid doses LD50 and LD100 (9.66 µg/mg and 11.72 µg/mg of body mass) were applied topically to insects under in vivo conditions and the hemolymph was collected after 24 and 48 h. To check the in vitro impact of the 2-octenoic acid, the examined fatty acid was given directly to the cultured hemocytes (to a final concentration: 0.33 and 0.16 µg/µl) and incubated for 24 and 48 h. Current research using fluorescence microscopy and spectrofluorimetric measurements indicates the death of immunocompetent cells via the apoptosis pathway. Moreover, it shows the activation of caspases and an increase in the level of reactive oxygen/nitrogen damage after both in vivo and in vitro treatment of 2-octenoic acid. This points to the impact of both cellular and humoral elements on the immunological response to the toxic compound. Hence, 2-octenoic acid seems to have significant potential as an insecticide while being safe for humans and the environment. Therefore, further research into its potential is warranted.