Introduction: Hypothyroidism is a chronic health condition which causes physical, cognitive and psychiatric symptoms. The prevalence of hypothyroidism in adults with intellectual disabilities is under researched. Method: Hypothyroidism was examined among 463 patients within an outpatient intellectual disability psychiatric team. Clinic records were utilised for this study, including sociodemographic, psychiatric and physical health diagnoses. Results: Among the 463 patients, 43 (9%) had hypothyroidism. Compared to those without hypothyroidism, the hypothyroid group were significantly older, more likely to be female, and had increased rates of high cholesterol, diabetes, Down's Syndrome and dementia. Discussion: Rates of hypothyroidism within this cohort of patients with intellectual disabilities were high (9%). The results suggest hypothyroidism in intellectual disability should be the focus of prospective research, in larger, more representative samples. This study indicates a need for increased awareness of, and resources for hypothyroidism in health services.