Background: Autistic adults face increased risks of anxiety, depression, and social isolation (Dennis et al., 2024), yet there remains a significant shortage of accessible mental health services that are tailored to their needs. Nature-based interventions (NBIs), structured therapeutic activities in natural settings (Shrestha et al., 2025; Tambyah et al., 2022), have shown promise in improving mental health and quality of life but remain underutilized in occupational therapy for this population. Objective: This capstone project explored how occupational therapy can support the mental health and well-being of autistic adults through the development, implementation, and evaluation of three 10-week nature-based intervention programs. The project aimed to highlight the therapeutic value of NBIs and advocate for their integration into occupational therapy mental health services. ACOTE Standards Addressed: This project aligns with ACOTE standards (d) Program Development and Evaluation (design and implement three NBI programs), (f) Advocacy (promote expanding OT roles in mental health for autistic adults), and (g) Education (educate occupational therapy practitioners on the benefits of NBIs and how these interventions can be integrated into practice). Methods: A mixed-methods design was employed to evaluate the effectiveness of nature-based interventions (NBIs) in enhancing mental health and quality of life and participant satisfaction with programming among autistic adults. Twenty-one participants engaged in three customized 10-week NBI programs across distinct social groups: Women’s Group (n = 3), Hiking Group (n = 5), and discoverLIFE (n = 15). Two individuals participated in multiple groups, with their data included in both of their respective group analyses. Quantitative outcomes were assessed using the GAD-7 and WHOQOL-BREF, with pre/post changes analyzed via Paired t-tests and Wilcoxon signed-rank tests in IBM SPSS 25. Post-intervention semi-structured individual and paired interviews with participants were thematically analyzed in NVivo 11. Informal reflections from group facilitators were gathered, and thematic analysis techniques were used to enhance the interpretation of formal data findings. Results: WHOQOL-BREF results for the overall sample indicated significant improvements in psychological health (p = .011, d = –0.61) and physical health (p = .049, d = –0.46), with increases in perceived quality of life (+7.41%) and health satisfaction (15.09%). The discoverLIFE group showed the most notable gains in both domains. GAD-7 scores significantly decreased across all three groups (p < .001), reflecting a reduction in anxiety symptoms across the overall sample. Qualitative findings supported these outcomes, with participants describing the nature-based activities as enjoyable and beneficial to their mental health. Many shared that symbolic elements in nature helped them apply session themes to everyday life. Facilitator reflections further reinforced these results, emphasizing the potential of NBIs to support the mental well-being and quality of life among autistic adults across diverse group settings. Conclusion: Findings suggest that NBIs offer the flexibility and adaptability to be implemented across various group settings and show strong potential to support the mental health and quality of life of autistic adults. This project demonstrates the potential for NBIs to be successfully integrated into occupational therapy practice, providing a valuable addition to mental health services. Further research is needed to understand their long-term impact and support broader use in practice.