Pain behaviors that are maintained beyond the acute stage after injury can contribute to subsequent psychosocial and physical disability. Critical to the study of pain behaviors is the availability of psychometrically sound pain behavior measures. In this study we developed a self-report measure of pain behaviors, the Pain Behaviors Self Report (PaB-SR). PaB-SR scores were developed using item response theory and evaluated using a rigorous, multiple-witness approach to validity testing. Participants included 661 survey participants with chronic pain and with multiple sclerosis, back pain, or arthritis; 618 survey participants who were significant others of a chronic pain participant; and 86 participants in a videotaped pain behavior observation protocol. Scores on the PaB-SR were found to be measurement invariant with respect to clinical condition. PaB-SR scores, observer reports, and the videotaped protocol yielded distinct, but convergent views of pain behavior, supporting the validity of the new measure. The PaB-SR is expected to be of substantial utility to researchers wishing to explore the relationship between pain behaviors and constructs such as pain intensity, pain interference, and disability.