Abstract: Objectives: This study assessed the long-term association between cultivated mindfulness and post-traumatic stress disorder (PTSD) symptom improvement following a 3-week intensive treatment program (ITP) for veterans. The aim was to determine whether changes in self-reported dispositional mindfulness were related to reduced self-reported PTSD and depression symptom severity, 6 months after participating in the ITP. Method: The sample comprised 288 veterans, 144 of whom completed follow-up surveys. The ITP integrated Cognitive Processing Therapy with mindfulness and yoga practices modeled off Mindfulness-Based Stress Reduction, delivered daily over the course of 3 weeks. Participants completed self-report measures at baseline, post-treatment, and 6-month follow-up. Linear mixed-effects regression models were employed to analyze the link between dispositional mindfulness changes and symptom severity. Results: Significant reductions in PTSD and depression symptoms occurred from baseline to the 6-month follow-up (effect sizes Cohen's d = 1.02 and 0.70, respectively). Dispositional mindfulness scores increased during treatment and were maintained at the at 6-month follow-up (effect size d = 0.36). Increased dispositional mindfulness was significantly related to lower PTSD and depression symptom severity. Changes in all four facets of dispositional mindfulness examined, especially Acting with Awareness and Non-judgement, were associated with 6-month follow-up PTSD severity, and all but Describe were associated with 6-month follow-up depression severity. Conclusions: This study provided evidence of the long-term association between self-reported mindfulness, cultivated in an ITP, and reduced PTSD and depression symptoms. Dispositional mindfulness was associated with enduring relief from trauma-related symptoms, emphasizing its potential role in sustaining treatment outcomes. This study highlights the potential of mindfulness practices in ITPs for veterans diagnosed with PTSD.