Background: Many adults with intellectual disabilities live a sedentary lifestyle, have low levels of functional fitness and are overweight. The purpose of this study was to determine whether an exercise intervention with activities which are simple, fun, accessible and adapted for socialising in a group would elicit significant improvements in various parameters associated with functional fitness for adults with intellectual disabilities. Methods: Forty-two adults with intellectual disability (44.5 ± 11.5 years) were randomly located to an exercise group (n = 19) and a control group (n = 23). The program consisted of walking, dancing, and resistance training exercises and was implemented, three times a week for 6 weeks. Results: Significant ameliorations (p < 0.05) were reported for body mass, hip circumference, aerobic capacity, functional ability, muscular strength, balance, and flexibility with varying degrees of effect sizes. p Conclusions: The combined exercise training program showed a significant positive impact on various parameters associated with functional fitness for adults with intellectual disability.