In the current report, a preliminary observation to study the adverse effects of the broad use acaricides fipronil (FPN) in rabbits infested with Psoroptes cuniculi. Two separate groups (5 rabbits/each) treated topically (poured on at the base of the neck) with fipronil 5%, 1 vial/ 10 kilogram body weight (kg bw) and 1 vial/ 5 kg bw. After FPN spot on application, rabbits in both groups examined microscopically on the 7th, 14th, and 28th day post treatment and the number of live mites (larvae, nymphs, and adults) on each rabbit counted at the end of the experiment (28th day). The results showed that the number of mites in rabbits topically treated with FPN did not show significant decrease, moreover a decrease in both treated rabbits body weight (bw) and in performance observed clearly, with some attendant mortality. In conclusion, this work showed that FPN was with limited efficacy on P. cuniculiand had some undesirable side effects. Further and in-depth studies on FPN toxicity in rabbits and other animals are necessary.