Objectives Psychologists play a pivotal role in meeting the mental health needs of people with intellectual disabilities. The aim of this study was to investigate the perceptions of Australian psychologists who work with adults with intellectual disabilities and mental ill health regarding their clinical competencies, workplace supports and training needs. Method One hundred and nine psychologists in Australia completed a self‐report online survey exploring clinical attitudes and practices when working with adults with intellectual disabilities and mental ill health. Provisional, generalist and clinical psychologists from a range of disability and non‐disability work settings were recruited. Results Findings revealed that provisional, generalist and clinical psychologists reported no significant differences in levels of agreement on self‐perceived clinical competencies in conducting mental health assessments. Psychologists in private practice and in non‐government organisations reported more adequate workplace resources to support mental health assessments for people with intellectual disabilities than did psychologists in government settings. Psychologists across work settings expressed similar views in self‐perceived clinical competencies and workplace training supports. The majority of psychologists reported limited formal academic training in intellectual disabilities and expressed a need for continual and specialised training in mental health and intellectual disabilities. Conclusions Implications for further training in mental health and intellectual disabilities highlight the need to cater to the specific needs of psychologists in the field.