Emotion regulation ideally promotes subjective well-being in addition to relieving distress. Mindfulness-to-Meaning theory (MMT) proposes that well-being interventions follow a common pathway to promote wellness using two intermediate stages: decentering from initial stress appraisals followed by positive reappraisal of life events-linking a broadened state of awareness with narrative meaning-making. A preregistered (https://osf.io/c2xzd) evaluation of the MMT compared online, 3-week adaptations of established well-being interventions in a postsecondary student sample. The study (N = 131) employed a four-arm randomized trial design, featuring (a) control, (b) mindfulness, (c) stress mindset, and (d) blended mindfulness and stress mindset training conditions. The MMT pathway accounted for change in well-being across all models, mindfulness training consistently promoted positive reappraisal despite an absence of reappraisal instructions, and an exploratory cross-lagged analysis found decentering facilitative of subsequent reappraisal. However, the stress mindset intervention failed to improve well-being relative to control, limiting capacity for causal inference; post hoc analyses, therefore, focused on the more efficacious mindfulness training conditions. The MMT accounted for change in well-being across all levels of analysis, although well-being changes were also supported by direct effects of mindfulness training and decentering, with only partial mediation through the complete MMT pathway. These findings support MMT as a process model for well-being but suggest that decentering and reappraisal only partially account for the salutary effects of well-being interventions. (PsycInfo Database Record (c) 2023 APA, all rights reserved).