The present work was undertaken to determine aqueous extract of mushroom (Pleurotus ostreatus) as an alternative to other coccidiosis control measures would result in improving body weight, oocyst reduction and improving pathological lesions of cecum. A total of 140 broiler chicks of 14 days age were divided into 7 groups (each contain 20 chicks). The 1^st group was not infected with Eimeria tenella and didn't take any medicine or additives and kept as control, while the 2^nd group was infected with Eimeria tenella at a rate of 50,000 sporulated oocyst/ml / bird at 14^th day of age. Third group was infected with Eimeria tenella as mentioned before at 14^th day of age and treated with aqueous extract of mushroom (200 mg/ml) at day 6 post infection and continued for 7 days consecutively. Fourth group was infected with E. tenella as mentioned before and treated with amprolium (200 mg/ml) at 6 day post infection and continued for 7 days consecutively.Fifth group was infected with E. tenella as mentioned before and treated with both aqueous extract of mushroom (200 mg/ml) and amprolium (200 mg/ml) at 6 day post infection, for 7 days. Sixth group was non infected with E. tenella but received aqueous extract of mushroom at 14^th day of age (200 mg/ml) and continued till the end of experiment (at 35 days of age). Seventh group not infected with E. tenella but received amprolium (200 mg/ml) at 14^th day of age and continued till the end of experiment (the period of experiment is three weeks). Body weight was recorded weekly, oocysts counted at 21, 28 and 35 days of age, and pathological lesions were studied at 28 and 35 days of age. The obtained data revealed that chicks of the 2^nd group showed a significant decrease in body weight, while third, fifth and sixth groups showed a significant increase in body weight which appeared clearly at 35day of age. Fifth group posses the highest body weight followed by chicks of sixth group then third group. The highest oocyst count was recorded in chicks of the 2^nd group while the lowest oocyst count was recorded in 5^th, 4th and 3^rd groups. Regarding pathological lesions, the infected and untreated 2^nd group showed severe necrosis of ceca with destruction and desquamation of the lining epithelium. The necrotic mucosa was heavily infiltrated or replaced with lymphocytes, macrophages and few heterophiles. The pathological lesions were less in the 3^rd group (infected and treated with mushroom) and nearly absent in both 4^th group (infected and treated with amprolium) and 5^th group (infected and treated with both mushroom and amprolium).