Accelerated experiential dynamic psychotherapy (AEDP; Fosha, 2000, 2021b) is an integrative, healing-oriented, mind–body, affect-focused therapy. A posttreatment outcome study demonstrated AEDP’s effectiveness (Iwakabe et al., 2020) on a variety of measures of psychological functioning. This study sought to address AEDP’s long-term effectiveness. As previously reported, 63 adult patients completed a 16-session AEDP treatment with qualified therapists in private practice in the United States, Canada, Israel, Japan, and Sweden. Forty patients responded to 6-month follow-up and 52 responded to 12-month follow-up. Results indicate that patients maintained their posttreatment therapeutic gains, both 6 and 12 months later. Large effect sizes (d = 0.74 to d = 1.60) both for reductions on measures of psychopathology (e.g., depression, negative automatic thoughts, experiential avoidance) and improvements on measures of positive mental health (e.g., well-being, self-compassion) were obtained. Patients with more pervasive and severe problems tended to have larger effect sizes (all ds > 1.0) and a larger proportion of them achieved clinically significant change over 6 and 12 months than patients with subclinical symptomatology. Piecewise growth modeling was used to confirm these results, with attrition over the follow-up period taken into account. Consistent with the above findings, piecewise growth modeling similarly showed that patients significantly improved from pre- to posttreatment and maintained gains from posttreatment through the 6- and 12-month follow-up. These results provide empirical support for the long-term effectiveness of AEDP for alleviating a variety of psychological problems and enhancing positive functioning.