Nature has the ability to heal many psychological wounds from anxiety and depression, stress, post traumatic stress disorder, and behavioral concerns. As a result, clinicians are recognizing the power of nature as a tool in the healing process. The purpose of this dissertation, which consists of one completed systematic review and a multiple probe single case study is to (a) provide background information on the current literature regarding nature, (b) create a manualized EcoWellness treatment intervention, and (c) test the effectiveness of the treatment intervention in order to provide practicing counselors with a potential new intervention to increase psychological wellbeing for those with a developmental disability. The systematic review lays the groundwork to identify the current research in the field of nature based counseling and what direction research needs to go. The intervention was implemented with young adults in a college setting who are diagnosed with neurodevelopmental disorder. The researcher used a single case multiple probe across participants design and visual analysis to determine if there was an effect when implementing the intervention. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]