Tobacco use is the leading cause of preventable death and disease (National Cancer Institute, 2017). Mindfulness-based interventions have been shown to improve emotional regulation, reduce stress, and support smoking cessation by targeting mechanisms underlying addiction and relapse (Keng et al., 2013; Guendelman et al., 2017). This secondary analysis examined whether participation in mindfulness-based smoking cessation interventions influenced smoking dependence, perceived stress, positive and negative affect, and self-compassion among adults attempting to quit smoking. Data was obtained from the iQuit Mindfully 2 × 2 randomized controlled trial (N = 504). Participants were randomized to one of four conditions: Usual Care, Mindfulness-Based Addiction Treatment (MBAT), iQuit Mindfully text messaging, or MBAT combined with iQuit Mindfully. Separate ANCOVAs were conducted to predict changes in smoking dependence, perceived stress, positive and negative affect, and self-compassion at weeks 8 and 24 from treatment condition, while adjusting for demographic characteristics, baseline outcome measures and smoking frequency, and smoking abstinence status. Across both the intent-to-treat and completers-only analyses, treatment conditions did not significantly affect psychosocial outcomes after adjustment for covariates. Instead, baseline values consistently emerged as the strongest predictors of follow-up outcomes. Smoking abstinence was associated with lower smoking dependence, reduced perceived stress, lower negative affect, and higher positive affect across both follow-up assessments. In conclusion, there were not significant differences in psychosocial variables based on treatment condition, but successfully quitting smoking predicted improved psychosocial functioning over time. Results emphasize the wide-ranging psychosocial benefits of smoking cessation.