ABSTRACT Background Intellectual disability and mental health disorders constitute a major health problem globally with higher economic burden in low- and middle-income countries such as Bangladesh. In 2017, the World Bank estimated that 85% of the global population lived in low-middle-income countries. Limited research has explored health practitioner knowledge and/or confidence in the diagnosis and treatment of mental health issues in persons with intellectual disabilities (IDs) in low-income countries such as Bangladesh. Method One hundred and ninety-seven Bangladeshi-based health practitioners were grouped into 7 main professional groups according the current Bangladeshi health hierarchy (psychiatrists; traditional healers and community workers; medical doctors; nurses; psychologists; allied health: speech therapists, occupational therapists, social workers; and others: teachers physiotherapists, administration staff). A 34-item online survey was completed, which included questions measuring symptoms of common mental health disorders with reference to the Psychiatric Assessment Schedule for Adults with Developmental Disabilities, and questions measuring confidence working with persons with IDs from the Therapy Confidence Scale-Intellectual Disabilities. Results Participants demonstrated low knowledge of symptomology but were “confident” working with people with IDs. Kruskal–Wallis H tests indicated a significant effect of professional group on both overall knowledge and confidence levels, respectively. Traditional healers and community health workers had significantly more knowledge of symptoms than all other practitioners for obsessive-compulsive disorder, depression, psychosis, and hypomania. Conclusion Participants demonstrated confidence, but low knowledge, in treating individuals with IDs. The development of training programs to address specific deficits in knowledge of mental health symptoms, and confidence in using assessment and assessment-based communication, is recommended.