Background: Little is known about the prevalence of depression and anxiety among older people with intellectual disabilities (ID). Therefore, the aim of this study was to study the prevalence of depression and anxiety in this population. Method: This study is a cross-sectional epidemiologic multicentre study which was part of the Healthy Ageing and Intellectual Disabilities study. The study population consisted of 990 participants aged ≥50 years with borderline to profound ID which were screened with self-report and informant-report instruments; 290 of them were assessed with a standardized diagnostic interview. Results: Depressive symptoms were prevalent in 16.8% (95% CI: 14.4-19.1) and significantly associated with higher age. Anxiety symptoms were prevalent in 16.3% (95% CI: 14.0-18.6) and significantly associated with female gender and borderline to mild ID. Major depressive disorder was prevalent in 7.6% (95% CI: 5.2-11.0), anxiety disorders in 4.4% (95% CI: 2.6-7.0) and both in 0.7% (95% CI: 0.2-1.6). There was no relationship with gender, age or level of ID. Limitations: For most participants, informant-report instruments have been used instead of self-report to overcome communication difficulties or inabilities. Also, a standardized psychiatric diagnostic interview has been used instead of psychiatric diagnoses made by an experienced psychiatrist. Conclusion: Prevalence of major depressive disorder is higher and of anxiety disorders lower than in the Dutch general older community-dwelling population. © 2012 Elsevier B.V. All rights reserved.