Aim: To translate and adapt the Health Assessment Questionnaire Disability Index (HAQ-DI) into Bengali (BHAQ) for use in Bangladeshi populations and to test its reliability and validity in patients with rheumatoid arthritis (RA). Method: The HAQ-DI was translated using rigorous forward-backward protocols and the translated version was subsequently cognitively pretested in a sample of 30 outpatients with RA. The pre-final version of the questionnaire was psychometrically tested for internal consistency and construct validity in a new sample of 100 consecutive RA outpatients. Results: Ten questions were changed to suit the Bengali culture. Pretests showed that the items included in the B-HAQ were well understood by Bengali patients, while some of the original items were difficult to understand for a majority of patients. The resulting B-HAQ showed good internal consistency and construct validity in the psychometric validation study. Conclusion: This study suggests that the B-HAQ is a reliable and valid instrument for measuring functional disability in a Bengali-speaking population with RA. Future studies should examine the test–retest reliability and responsiveness of the B-HAQ before it can be confidently recommended as an outcome measure in intervention studies.