Background: The number of people with intellectual disabilities and associated mental illness has increased considerably in recent years. This population presents greater obstacles than their peers without mental health problems in accessing education, leisure, and health services. This, conditions their quality of life (QoL) and makes them one of the most vulnerable groups in society. Methods: This study seeks to know the level of QoL of 181 people with intellectual disabilities and mental health problems between the ages of 35 and 75, based on the perceptions of the professionals who work with them in different disability care services in Chile. The data were collected with the FUMAT scale. Findings: The dimensions of self-determination and personal development obtained the lowest scores. In addition, living in rural settings, receiving regular support, or being a man was associated with a better QoL. Conclusions: It would be desirable to increase the frequency with which certain supports aimed at the population with intellectual disabilities and mental health problems are provided. Likewise, the exercise of informed and meaningful choices must be encouraged.