Objectives:It is not known whether psychosocial chronic pain treatments produce benefits through the unique mechanisms specified by theory. Fundamental to gaining an accurate understanding of this issue is to first determine whether the most widely used process measures assess unique constructs and predict unique variance in pain outcomes. This study examined the associations between the Pain Catastrophizing Scale (PCS), Five-Facet Mindfulness Questionnaire (FFMQ-SF), and the Chronic Pain Acceptance Questionnaire (CPAQ-8), and determined their unique contributions to the prediction of pain intensity, pain interference, and depression.Methods:A cross-sectional study was conducted with undergraduate students (N=260) reporting chronic or intermittent pain. Correlations, regression models, and multiple mediation models were performed. Relevant covariates were included.Results:The PCS, FFMQ-SF scales, and CPAQ-8 were correlated in mostly expected directions, but not so highly as to indicate redundancy. The PCS significantly predicted pain intensity, interference, and depression. The FFMQ-SF Observing and Describing scales predicted pain intensity; Nonreactivity and Nonjudging significantly predicted interference and depression, respectively. The CPAQ-8 was not a significant predictor in any of the regression models. The PCS was a comparatively stronger mediator than the FFMQ-SF scales in the intensity to interference, and intensity to depression mediation models.Discussion:The findings indicate that pain catastrophizing, mindfulness, and pain acceptance are related, but unique constructs. The PCS and select FFMQ-SF scales were uniquely associated with the criterion measures. However, the PCS emerged as the most robust process, highlighting the importance of targeting this cognitive domain in streamlining pain treatments to optimize outcome.