Several case studies describe utilizing combined approaches to treating individuals with co-occurring obsessive-compulsive disorder (OCD) and posttraumatic stress disorder (PTSD), yet empirical support for concurrent approaches is lacking. Further, no study has described a combined exposure and response prevention (ERP) and prolonged exposure (PE) approach despite theoretical and implementation similarities. Given the noted challenges in treating co-occurring OCD and PTSD, particularly in cases of dynamic comorbidity, the current study sought to provide empirical support for concurrent ERP+PE in a small sample of individuals diagnosed with co-occurring OCD and PTSD. Retrospective data was analyzed from eight patients (87.5% dynamic comorbidity) who underwent concurrent ERP+PE in a behavioral health hospital system. Effectiveness of ERP+PE was comparable to previous research on the separate treatments; patients experienced an average reduction in Yale-Brown Obsessive-Compulsive Scale-Self-Report scores of 11.75 and PTSD Checklist scores of 22.50, effect sizes of 1.65 and 1.44, respectively. Broadly, these preliminary findings suggest that a concurrent approach to treating co-occurring OCD and PTSD is effective even with dynamic comorbidity and that concurrent ERP+PE, specifically, yields promising treatment outcomes. The current study provides a foundation for future exploration of other treatment types and approaches. Replication of findings in larger, prospective samples is needed.