Background and Objectives: Finding the relationship between the joints range of motion and swimming time is important, so the aim of the present study was to investigate the relationship between the joints range of motion and time of 50, 100 and 200m breaststroke swimming in 12-13 years elite swimmer boys. Materials and Methods: In this descriptive study, subjects were selected from 111 elite swimmers, 12-13 years old, participated in the national championship of the country selection in 2016 in Tehran, 31 participants in 50m breaststroke, 29 participants in 100m breaststroke and 23 participants in 200m breaststroke. Joints range of motion was measured by Rydkov questionnaires. Pearson᾽ s correlation coefficient was used to examine the relationship between the variables. Results: There was a significant negative relationship between shoulder hyperextension and time (r=-0. 390, p=0. 030) in 50m breaststroke. There was a significant negative relationship between ankle plantar flexion and time (r=-0. 384, p=0. 040) in 100m breaststroke. There were significant negative relationships between neck flexion and time (r=-0. 446, p=0. 033) and shoulder hyperextension and time (r=-0. 467, p=0. 025); whereas there was a significant positive relationship between hip flexion and time (r=0. 414, p=0. 049) in 200m breaststroke. There was no significant difference between 50, 100 and 200m breaststroke swimming (p>0. 05). Conclusion: The results showed that there was a significant relationship between the joints range of motion and 50, 100 and 200m breaststroke time. So, it is recommended that coaches pay attention to the studies in this field for choosing swimmers at the early teens to save time and money through proper choice and substitution of talented swimmers and gain more success in reaching the peak of athletic performance.