Deltamethrin is a newer class of insecticide used on crops, pets, and livestock, in home pest control, and malaria vector control belonging to the synthetic pyrethroid group, which is being promoted in the place of organophosphate compounds due to the harmful and persistent effects of the latter. Unfortunately, as its usage increased, so has the number of poisoning cases associated with deltamethrin. Fortunately, the mortality in deltamethrin poisoning cases is low. However, deltamethrin poisoning causes signs and symptoms similar to the clinical features of organophosphate poisoning. This case report is of a 20-year-old man who consumed an unknown substance in a suicidal attempt and presented with clinical signs of organophosphate toxicity. Later the compound was identified as deltamethrin. This case report adds to the medical literature on deltamethrin poisoning. It showed that apart from the similarity in their clinical features in toxicity, deltamethrin can even give a positive result on atropine challenge tests like organophosphate and that the fasciculations induced by deltamethrin may be temporary. This case report will also benefit the clinician in unknown compound poisoning cases as it shows that the clinician can suspect deltamethrin toxicity alongside organophosphate toxicity in the differential diagnosis when the atropine challenge test gives a positive result.