Aquatic strengthening exercise is recommended for people with hip joint replacement; however, limited studies and inconsistent results were founded. Primary disability of hip joint replacement is caused by osteoarthritis. Exercise is vital for managing and preventing the joint functional movement limitations. The aim of the study is to examine the effects of aquatic exercise on strength and range of motion after hip joint replacement. A woman undergoing primary hip joint replacement (age, 44) participated in aquatic strengthening exercise over 12 weeks. Isokinetic testing was collected to monitor average torque, average work, average power and range of motion after hip joint replacement. Data were collected before surgery and after 3 months of aquatic strengthening exercise. Repeated measures analysis of variance showed that aquatic strengthening exercise improved both hip muscles strength and range of motion. Beneficial short-term effects of aquatic strengthening exercise were found after hip replacement