Acceptance of chronic pain is emerging as an important concept in understanding ways that chronic pain sufferers can remain engaged with valued aspects of life. Recent studies have relied heavily on cross-sectional investigations at a single time point. The present study sought to prospectively investigate relations between acceptance of chronic pain and patient functioning. A sample of adults referred for interdisciplinary treatment of severe and disabling chronic pain was assessed twice, an average of 3.9 months apart. Results showed that pain and acceptance were largely unrelated. Pain at Time 2 was weakly related to measures of functioning at Time 2. On the other hand, acceptance at Time 1 was consistently related to patient functioning at Time 2. Those patients who reported greater acceptance at Time 1 reported better emotional, social, and physical functioning, less medication consumption, and better work status at Time 2. These data suggest that willingness to have pain, and to engage in activity regardless of pain, can lead to healthy functioning for patients with chronic pain. Treatment outcome and process studies may demonstrate the potential for acceptance-based clinical methods for chronic pain management.