The main purpose of this study is to explore the effects of Tee Ball teaching intervention on the health-related fitness of people with mental retardations. A total of 20 people with severe mental retardation enrolled in a welfare service institution for the disabled in Pingtung was selected to participate in this study. The subjects were taught Tee Ball for twelve weeks and 120 minutes for each time. Body Mass Index, upper and lower body strength, and aerobic endurance were tested according to the national physical fitness evaluation. Descriptive statistics and paired-sample t-test were to analyze the quantitative data obtained from this study. Statistical analyses were carried out using SPSS. Results showed that the upper body strength and aerobic endurance of the users with mental retardations have been significantly improved after twelve weeks of Tee Ball training. It was suggested that this exercise program could be used as a rehabilitation tool to help improve the quality of life and physical wellbeing of disabled people.