Introduction: Participating in sports programs increases physical and mental health and fitness. The purpose of this study was to assess the physical fitness of persons with intellectual disability (ID) who participated in Special Olympics Iran, and comparing with their counterparts who did not participate in the these matches.Materials and Methods: The research sample included 138 boys with ID in two groups, athletes (70 boys with ID with and without Down’s syndrome) and non-athletes (68 boys with ID with and without Down’s syndrome), aged 18 to 30 years. To assess physical fitness, a set of Eurofit special tests, including explosive leg strength (standing broad jump test), arm strength (pushing a 2 kg ball test), abdominal muscle endurance (sit-up test), speed (20 meter run test), flexibility (sit and reach test), and balance (walk on a bench test) were used. To compare two groups, independent t test for variables of explosive leg strength, abdominal muscle endurance, and speed, and also Mann-Whitney U statistical method for variables of arm strength, flexibility, balance, and body mass index (BMI) were used at a significant level of P < 0.050.Results: There were significant differences in variables of flexibility (P = 0.035), abdominal muscle endurance (P = 0.034), explosive leg strength (P = 0.025), and speed (P = 0.009) between athlete and non-athlete boys with ID with and without Down’s syndrome. Moreover, there were significant differences in BMI (P = 0.041) and speed (P = 0.001) between athlete and non-athlete boys with ID without Down’s syndrome, and also in flexibility (P = 0.030), abdominal muscle endurance (P = 0.001), explosive leg strength (P = 0.001), and speed (P = 0.002) between athlete and non-athlete boys with Down’s syndrome.Conclusion: According to the results, the participants in Special Olympics Iran had a better level of physical fitness than those without this experience. Therefore, Special Olympics programs are recommended as an effective factor in improving the physical fitness of boys with ID.