This study examined psychosocial pain treatment moderation in a secondary analysis of a trial that compared cognitive therapy (CT), mindfulness-meditation (MM), and mindfulness-based cognitive therapy (MBCT) for chronic low back pain (CLBP). The Limit, Activate, and Enhance (LA&E) model of moderation provided a framework for testing a priori hypotheses. Adult participants (N = 69) with CLBP completed a pretreatment assessment of hypothesized moderators: pain catastrophizing, brain state as assessed by electroencephalogram, mindful observing, and nonreactivity. Outcomes were pain interference, characteristic pain intensity, physical function, and depression, assessed at pre- and post-treatment. Moderation analyses found significant interaction effects, specifically: 1) higher and lower baseline pain catastrophizing was associated with greater improvement in pain intensity in MM and MBCT, respectively; 2) higher baseline theta power was associated with greater improvement in depression in MBCT and interfered with response to CT; 3) lower baseline nonreactivity was associated with greater improvement in physical function in MM while higher nonreactivity was associated with greater improvement in MBCT. The findings support the possibility that different patients are more or less likely to benefit from various treatments. Theory-driven moderation research has the capacity to inform the development of patient-treatment matching algorithms to optimize outcome. PERSPECTIVE: This study presents preliminary findings from theory-driven tests of the moderators of mindfulness meditation, cognitive therapy, and mindfulness-based cognitive therapy for chronic low back pain. The results of such analyses may inform the understanding of for whom various evidence-based psychosocial pain treatments may engender the most meaningful benefits.