Brief interventions focused on targeting malleable risk factors provide several advantages over traditional treatments for PTSD including increased acceptability and affordability. Anxiety sensitivity (AS) has been established as a rapidly modifiable risk factor, and therefore, a promising target for brief interventions. The current study conducted secondary analyses to data from a larger clinic trial to examine the impact of a brief AS-focused and control interventions on changes in PTSD overall symptoms and symptoms clusters over a one-year period. Changes in the specific AS facets (cognitive, physical, social) on changes in PTSD symptoms were also examined. Adult participants (N = 304) with elevated levels of transdiagnostic risk factors including AS were recruited from the community to participate in a randomized clinical trial of brief web-based interventions. Participants completed assessments at baseline, post-treatment, Month 1, Month 3, Month 6, and Year 1. Results indicated significant effects in both AS and control conditions, with significantly greater PTSD symptom improvement over time for those completing the AS-focused intervention. Additionally, reductions in AS and the AS cognitive subscale from baseline to post-treatment mediated the effect of condition on changes in PTSD symptoms from baseline to Month 1. These findings suggest that a brief, computerized AS intervention was efficacious for reducing PTSD symptoms. The purported mechanism of action (reduced AS) was supported. Intervention effects were durable as they were maintained at one-year follow-up, although these warrant further investigation given the small sample at Year 1. In conjunction with prior research, findings suggest that the AS intervention may address some barriers to traditional treatments given its brevity, convenience, and efficacy. Limitations regarding heterogeneity and size of the sample are discussed.