This study aims to investigate the effect of traditional sports in order to improve physical fitness of young athletes. Researchers adopted an 11-week randomized controlled trial design. Participants included young athletes from Sultan Ageng Tirtayasa University (Indonesia) who were allocated to TSG (n = 20) and CG (n = 20). Analysis of Students’ t-tests for paired samples used to test differences in physical fitness among males and females in two groups at the pre-test and post-test stages. The effect size test (Cohen’s d) was used in this research. The first findings showed that male participants in TSG had differences in physical fitness in the pre-test and post-test stages related to Multi-stage (p < 0.001, d = −2.17), Shuttle run: 4×10 meters (p < 0.001, d = 2.43), 30 meter run test (p < 0.001, d = 1.85) and sit and reach test (p = 0.002, d = −1.41), while male participants in CG had differences in physical fitness in terms of Shuttle run: 4 ×10 meters (p < 0.001, d = 1.69), Run test 30 meters (p < 0.001, d = 1.64), but no differences were found for other components. The second finding showed that female participants in TSG had differences in physical fitness in the pre-test and post-test stages related to Multi-stage (p < 0.001, d = −1.53), Shuttle run: 4×10 meters (p < 0.001, d = 2.76), 30 meter Run test (p < 0.001, d = 2.02) and Sit and reach test (p < 0 .001, d = −1.72), while the female participants in CG had differences in physical fitness in the 30 meter Run test (p < 0.001, d = 2.87), but no differences were found for the other components. In conclusion, this research proves that traditional sport for 11 weeks can improve the physical fitness of young athletes.