The effect of exposing Triatoma infestans to chickens treated with Cypermethrin pour-on combined with piperonyl butoxide (PBO) was studied. Four groups of treated chickens and one control group were used. Each treatment received 1 or 2 ml of the Cypermethrin formulation with and without PBO. Independent groups of nymphs were fed 1, 7, 15, 30, and 45 d after the treatment application. Blood intake was estimated after each feeding occasion. Up to 15 d after the pour-on application, high mortality was observed in all nymphs fed on treated chickens (>93%±12), and lower than the nymphs of the control group (<33%±15). After 30 d of the pour-on application, there was significantly different mortality between the treatment with 1 ml (80%±9) and 2 ml (>96%±5); no difference was observed between groups with or without PBO addition. After 45 d of the pour-on application, the treatments did not show significant differences (77%±7), although all treatments showed higher mortality than the control group (10%±9). Up to 45 d after the pour-on application, blood intake by nymphs exposed to treated chickens (0.85±0.96 mg/nymph) was lower than blood intake by nymphs exposed to control chickens (6.7±5 mg/nymph). This study shows that Cypermethrin pour-on produces high mortality and reduces the blood intake of third-instar nymphs of T. infestans up to 45 d after the insecticide application to chickens. PBO did not produce a detectable effect.