Background The aim of this study was to investigate the effects of a vocational rehabilitation group intervention on motivation and occupational self-competence in individuals with intellectual disability. Methods A single-blind, randomised controlled study design was used. The intervention group (IG) received the group-based intervention alongside the individualised vocational rehabilitation (IVR) and the control group (CG) continued receiving only the IVR for 8 weeks. In order to assess motivation and occupational self-competence, Objective Achievement Motivation Test (OLMT) and Occupational Self-Assessment (OSA) were used. Results Forty-nine individuals were enrolled to the study and randomised into IG (n = 24) and CG (n = 25). Two groups were similar at baseline in terms of demographic qualities, OLMT and OSA scores (p > 0.05). After the intervention, the IG showed significant improvements in all assessments (p < 0.05), however the CG showed improvements only in OLMT sub-tests (p < 0.05). Conclusions The group-based intervention program was effective in increasing occupational self-competence and motivation.