Abstract: Treatment for active-duty service members or veterans who have posttraumatic stress disorder (PTSD) symptoms has proven to be challenging due to stigma, lack of engagement, an overwhelmed health system, and lack of evidence-based treatments that are appropriate for a population who tends to believe formal therapy is not helpful. The purpose of this study was to examine how hiking, a form of outdoor recreation therapy, may impact symptoms of PTSD, specifically anxiety, in U.S. active-duty service members. This study is a secondary analysis of data from a recent original research study (Walter et al., 2023). The original research study was a randomized, controlled, double-blind trial assessing a group of participants (N = 96) who had been diagnosed with major depressive disorder at the following time points: before and after the 6-week intervention program, before and after each individual hiking intervention session, and 3 months postintervention completion. This secondary analysis study examined the effectiveness of a hiking intervention to reduce symptoms of anxiety in those who have been diagnosed with major depressive disorder (N = 48). Results indicate an improvement in anxiety symptoms following participation in an outdoor hiking program for those who already had an existing diagnosis of anxiety prior to beginning the hiking program. For those who did not have a diagnosis of anxiety prior to the study, the hiking program did not affect symptoms. The outcome of this study suggests that an outdoor hiking program may have a positive impact on anxious symptoms and may be used as an adjunct therapy for service members.