Objective: A growing body of evidence suggests that chronic pain patients suffer from chronic self-regulatory fatigue: difficulty controlling thoughts, emotions, and behavior. Pain acceptance, which involves responding to pain and related experiences without attempts to control or avoid them (pain willingness), and pursuit of valued life activities regardless of pain (activity engagement) has been associated with various favorable outcomes in chronic pain patients, including better psychological functioning. The study presented here tested the hypotheses that pain acceptance is associated with less psychological distress, higher psychological well-being, and reduced self-regulatory fatigue in temporomandibular disorder (TMD) patients, particularly for those with longer pain duration. Methods: Cross-sectional data were provided by 135 TMD patients during an initial evaluation at a university-based tertiary orofacial pain clinic. Results: Results of hierarchical linear regression models indicated that, controlling for pain severity, pain willingness is associated with less psychological distress and lower self-regulatory fatigue, and activity engagement is associated with greater psychological well-being. Furthermore, the effect of pain willingness on psychological distress was moderated by pain duration such that pain willingness was more strongly associated with less psychological distress in patients with longer pain duration; this moderating effect was fully mediated by self-regulatory fatigue. Conclusion: These findings suggest pain willingness may buffer against self-regulatory fatigue in those with longer pain duration, and such conservation of self-regulatory resources may protect against psychological symptoms. (PsycINFO Database Record (c) 2012 APA, all rights reserved).