The house fly, Musca domestica L. (Diptera: Muscidae), is a major pest of medical and veterinary importance all over the world. Management efforts for house flies are usually compromised owing to their resistance to many groups of conventional insecticides. Cantharidin, a natural toxin produced by meloid beetles, is a biopesticide with a reported toxicity to some insect pests including house flies. However, the effects of cantharidin on biological and fitness parameters of house flies have not yet been investigated. In the present study, we investigated the toxicity and sublethal effects of cantharidin on biological parameters of house flies for two consecutive generations. The results revealed that the values of LC_50, LC₂₅, LC₁₀, and LC₂ against house flies were to be 2.45, 1.23, 0.66, and 0.30 mg/ liter, respectively. Sublethal effects of these concentrations on the development and reproduction parameters of house flies revealed that cantharidin reduced population growth by affecting pupation rate, adult emergence, and by lengthening developmental time. The female ratio, fecundity, egg hatching, and survival of adult flies were significantly reduced at LC_2, LC₁₀, LC₂₅, and LC₅₀ of cantharidin when compared with the control group. Furthermore, the increase in concentration of cantharidin had a significant effect on reducing the mean values of mean relative growth rate, net reproductive rate (R_o), intrinsic rate of natural increase (r_m), and biotic potential (bp). In conclusion, the results of this study revealed the toxicity of cantharidin against house flies and the adverse effects of sublethal concentrations on biological parameters which may have positive implications for effective management of house flies.