Objective: Posttraumatic stress disorder (PTSD) is a major public health concern. Although effective treatments exist, affected individuals face many barriers to receiving traditional care. Smartphones are carried by nearly 2 thirds of the U.S. population, offering a promising new option to overcome many of these barriers by delivering self-help interventions through applications (apps). As there is limited research on apps for trauma survivors with PTSD symptoms, we conducted a pilot feasibility, acceptability, and potential efficacy trial of PTSD Coach, a self-management smartphone app for PTSD. Method: A community sample of trauma survivors with PTSD symptoms (N = 49) were randomized to 1 month using PTSD Coach or a waitlist condition. Self-report assessments were completed at baseline, postcondition, and 1-month follow-up. Following the postcondition assessment, waitlist participants were crossed-over to receive PTSD Coach. Results: Participants reported using the app several times per week, throughout the day across multiple contexts, and endorsed few barriers to use. Participants also reported that PTSD Coach components were moderately helpful and that they had learned tools and skills from the app to manage their symptoms. Between conditions effect size estimates were modest (d = −0.25 to −0.33) for PTSD symptom improvement, but not statistically significant. Conclusions: Findings suggest that PTSD Coach is a feasible and acceptable intervention. Findings regarding efficacy are less clear as the study suffered from low statistical power; however, effect size estimates, patterns of within group findings, and secondary analyses suggest that further development and research on PTSD Coach is warranted.