Introduction: Children with developmental disabilities and people with disabilities can face various challenges when performing sports activities. For this reason, it is necessary to motivate them and include them. Swimming emerges as an adequate choice due to its benefits to the holistic health of the individual and adaptation to individual needs, which enables inclusion regardless of impairment or disability. Objectives: The main goal of this research is to evaluate the effectiveness of a 12 - week swimming program on cardiorespiratory endurance and muscle strength in children with developmental disabilities and people with disabilities. The specific objectives are to examine the effect of three-month swimming training on cardiorespiratory endurance and muscle strength regarding gender, age and disability. Subjects and methods: 30 subjects participated in the research, i.e. children with developmental disabilities and persons with disabilities, aged 11 to 30, of which 26 were men and 4 were women. They participated in a swimming program twice a week for 12 weeks. The 6-minute walking test for cardiorespiratory endurance and dynamometry for muscle strength were used to determine the outcome of the research. Results: A statistically significant increase in the 6-minute walk test was found for SpO2, heart rate and distance. There is no statistically significant difference in blood pressure. Also, a statistically significant increase in the muscle strength of 8 groups of skeletal muscles was determined. There was no statistically significant difference regarding the age, gender and disability of the respondents. Conclusion: Swimming has a significant effect on increasing muscle strength in children with developmental disabilities and people with disabilities, while cardiorespiratory endurance needs to be further analyzed. Future studies should consider sample size and control and experimental groups.