An experiment was carried out to examine the effect of dietary supplementation with Olympus tea (Sideritis scardica) on the performance of broiler chickens challenged with 6 × 10⁴ sporulated oocysts of Eimeria tenella at 14 days of age. A total of 150 day-old Cobb-500 chickens were separated into 5 equal groups with three subgroups each. Two of the groups, one challenged with E. tenella and the other not, were given the basal diet and served as controls, two challenged groups were administered diets supplemented with ground dried plants of Olympus tea at levels of 5 and 10 g/kg of diet, and the remaining challenged group a diet supplemented with the coccidiostat lasalocid. During the experimental period that lasted 35 days, body weight and feed intake were weekly recorded, and feed conversion ratio were calculated. Following the E. tenella challenge on day 14 of age, mortality, caecal lesion score, bloody diarrhoea and oocyst excretion were examined in all groups from day 17 to day 26 of age. Results showed that mean body weight gain of the Olympus tea groups, although higher (P<0.05) than the challenged control group, were lower (P<0.05) compared to the non-challenged control and lasalocid groups. Feed conversion ratio of the challenged control group was the highest (P<0.05) among all groups. Data on the extent of bloody diarrhoea, mortality, caecal lesion score and oocyst output suggested that treatment with Olympus tea at the supplementation level of 10 g/kg diet in particular, could alleviate the impact of parasite infection on the bird by exerting a coccidiostatic effect against E. tenella which, however, was considerably lower than that exhibited by lasalocid.