Background Generalist mental health professionals are inadequately equipped to meet the rights of people with intellectual disability. A better understanding of the attributes of effective professionals may assist in the development of workforce capacity in this area. Methods Twenty‐eight family/support persons of people with intellectual disability participated in four focus groups. Thematic analysis was undertaken applying the Intellectual Disability Mental Health Core Competencies Framework. Results Participants described attributes that aligned with current professional expectations such as working together and new attributes such as differentiating between behaviour and mental health. An unexpected finding was the need for professionals to be able to infer meaning by interpreting multiple sources of information. Participants also wanted professionals to acknowledge their professional limitations and seek professional support. Conclusion Family/support persons identified a range of attributes of effective mental health professionals to support people with intellectual disability. Further research is necessary, particularly from the perspective of people with intellectual disability.