The purpose of this study is to examine the effects of adapted play activities on physical fitness in individuals with autism spectrum disorder (ASD). In this study, the pretest-posttest design with a single experimental group was used. The sample of the study is comprised of 7 students with 7-13 years of age. In the measurement of physical fitness parameters of children with ASD, height, body weight, flexibility, vertical jump, and right/left hand grasping power tests were performed. SPSS 23.0 program was used. In addition to descriptive statistics, Wilcoxon signed rank test was used in the comparisons of pretest-posttest measurements. According to the findings of the research, among the physical fitness parameters, it was determined that there were statistically significant differences in the flexibility, vertical jumping, right and left-hand grasping power values, while there was statistically no significant difference concerning the body mass index values. We can mention that the obtained findings demonstrate that play activities lesson program has positive impacts on the physical fitness parameters of children with ASD, and it contributes to their motor developments. Additionally, this research study is considered significant since it leads the way for researchers and teachers of this field and it provides an insight for further studies.