The Brief Pain Inventory (BPI) is a questionnaire developed to assess the severity of pain and the impact of pain on daily function. The purpose of the current study was to evaluate the psychometric properties of the BPI for use in patients undergoing cardiac surgery. Between September 2004 and September 2005, 534 patients completed the BPI before surgery and 462 responded six months after surgery. The BPI was validated with respect to construct validity, internal consistency, criterion validity, and responsiveness. To evaluate the criterion validity, the BPI was validated against the bodily pain (BP) scale of the Medical Outcomes Study Short-Form Health Survey (SF-36). The factor analysis resulted in two distinct factors, supporting the validity of the two-factor structure of the original BPI, with high loadings on pain severity and pain interference. Results indicated acceptable internal consistency, with Cronbach's alpha coefficients between 0.84 and 0.94. The association between the BPI and the SF-36 BP dimension supported the criterion validity, with correlation coefficients between 0.47 and 0.65. The pain severity scale and the pain interference scale declined from baseline to follow-up. These results supported the responsiveness of the BPI. The study confirmed that the BPI shows good psychometric properties of reliability, validity, and responsiveness, enabling it to be used to measure pain in patients after cardiac surgery. Validating pain measures for use in this population is an important part of establishing a foundation for future studies on chronic pain after cardiac surgery.