Background Depression and anxiety are amongst the most prevalent mental health disorders in the older population with intellectual disability (ID). There is a paucity of research that pertains to associative biopsychosocial factors for depression and anxiety in this population. The aim of this study is to determine the biopsychosocial factors associated with depression and anxiety in a population of older adults with ID in Ireland. Methods The study was part of ‘The Intellectual Disability Supplement to The Irish Longitudinal Study on Ageing’. Depressive symptoms were assessed using the Glasgow Depression Scale for people with a Learning Disability. Anxiety symptoms were measured using the Glasgow Anxiety Scale for people with a Learning Disability. The cross‐sectional associations of depression and anxiety with biopsychosocial parameters were measured using a variety of self‐report and proxy‐completed questionnaires. Results For the study population, 9.97% met the criteria for depression, and 15.12% met the criteria for an anxiety disorder. Participants meeting criteria for depression were more likely to be taking regular mood stabiliser medications and to exhibit aggressive challenging behaviour. Participants meeting criteria for anxiety were more likely to have sleep difficulties and report loneliness. Participants meeting criteria for either/both depression and anxiety were more likely to report loneliness. Conclusions This study identified both treatable and modifiable, as well as unmodifiable, biopsychosocial factors associated with depression and/or anxiety in older adults with ID. A longitudinal study follow‐up will further develop our knowledge on the causality and direction of associated biopsychosocial factors with depression and anxiety in older adults with ID and better inform management strategies, prevention policies and funding of services.