This paper analyses job satisfaction and differences in factors affecting it among workers with an intellectual disability and mental illness (MI) depending on their work regime [special employment regime (SER) or occupational service (OS)]. To do so, answers were analysed from 874 participants on a Job Satisfaction Scale used in sheltered workshops in Spain. The results indicate that job satisfaction among workers with intellectual disability and MI in both the SER and the OS regimes is high, with the highest job satisfaction deriving from the Items of communicating problems to resolve them. The lowest levels of job satisfaction are related to the opportunity to take decisions and participate at work. In the majority of the Items analysed, no differences were found on the basis of the age groups considered nor the gender of the participants.