Perseverative thought (PT) is a major mechanism of anxiety and related forms of psychopathology. Although mindfulness-based interventions show promise for reducing PT, treatment development is hindered by an incomplete understanding of the relationships between dissociable facets of mindfulness (present-moment awareness; nonjudgment of experience; nonreactivity to experience) and those of PT (worry; rumination; shared perseverative tendencies). The present study tested and replicated hypothesized relationships between facets of PT and mindfulness in three well-powered, independent samples (N = 289 undergraduate; N = 255 crowdsourced; N = 261 anxious/depressed community). Consistent with predictions, greater present-moment awareness incrementally predicted lower transdiagnostic PT, as did nonjudgment and nonreactivity. Nonreactivity was specifically inversely related to trait worry (i.e., beyond variance shared with transdiagnostic PT, rumination, and other mindfulness facets), while nonjudgment was specifically related to rumination (brooding). Findings replicated across all samples. In two samples, greater present-moment awareness unexpectedly predicted higher worry when other facets were controlled. Taken together, findings establish and replicate a link between present-moment awareness to general perseverative tendencies, with specific inverse relationships of nonreactivity and nonjudgment to worry and rumination, respectively. Future experimental research should test hypothesized causal pathways to inform theoretical models and development of transdiagnostic and personalized treatments.