Background: Soccer is the world's most popular sport. The present authors evaluated the effect of the Game of Life (GOL) soccer initiative on soccer skills, fitness and mobility of adults with intellectual disability (ID) and autism spectrum disorder (ASD). Methods: The programme is comprised of once-weekly sessions. Outcomes: soccer skills, fitness and mobility. Effectiveness was evaluated using within-/between-group analyses (e.g. effect size, ES). Results: Fifty adults with intellectual disability and 19 with ASD (age = 31.80 ± 10.11) participated in this study. From pre-test to post-test, the intellectual disability group improved their soccer skills (ES = 0.437); physical fitness--the intellectual disability group presented trivial ESs, whereas the ASD group showed moderate-to-large ESs; Mobility--only the ASD group presented a significant improvement (ES=-0.435), and the intellectual disability group presented better ability in most outcomes in pre- and post-tests. Conclusion: The findings indicated differences in entry-level performance and training impact between the two groups. This should be considered when developing training programmes for soccer players.