This randomized controlled trial examined the impact of a psychoeducational group program on the mental well-being of unit-based nurse leaders, specifically nurse managers and assistant nurse managers. The program was developed around the themes of resilience, insight, self-compassion, and empowerment to fight burnout and enhance purposeful adaptive coping to reduce distress and improve mental wellbeing. The sample included 77 unit-based nurse leaders. Outcomes included post-traumatic growth, resilience, insight, self-compassion, empowerment, perceived stress, burnout, and job satisfaction. Paired samples t-tests and repeated measures ANOVA tests were conducted to compare outcomes at baseline to the follow-up timepoints of endpoint, one-month follow-up, three-month follow-up, and six-month follow-up. The intervention group participants showed significant improvement in post-traumatic growth between baseline and all follow-up timepoints compared to the waitlist control group. Among intervention group participants, there were also significant improvements in self-reflection and insight, self-compassion, psychological empowerment, and compassion satisfaction, as well as significant reductions in perceived stress, burnout, and secondary traumatic stress. This study extends existing evidence that this psychoeducational group program can be an effective intervention for improving and protecting mental wellbeing. Among nurse leaders, it can reduce stress and burnout and improve post-traumatic growth, self-reflection and insight, self-compassion, psychological empowerment, and compassion satisfaction.