To explore whether continuous positive airway pressure (CPAP) adherence among adult patients with obstructive sleep apnea (OSA) and posttraumatic stress disorder (PTSD) affects the PTSD Checklist (PCL), a validated tool that measures severity of PTSD symptoms. Studies focusing on PTSD and OSA were searched in PubMed and CINAHL databases. Inclusion and exclusion criteria were applied, decreasing the article yield to nine. All articles chosen focused on the adult population and were conducted in North America. The literature review yielded eight observational cohort studies and one descriptive study. Seven studies were conducted with Veterans and all studies used the PCL tool. Three themes were identified: (a) Trauma and OSA, (b) OSA and PTSD Symptoms, and (c) CPAP Therapy and PTSD Symptoms. An area of further study is assessing how CPAP adherence might affect improvement in PTSD symptoms and how adherence can be improved. OSA is correlated with more severe PTSD symptoms, but CPAP use is associated with improvement in PTSD symptoms. The literature reviewed found PCL scores improved up to 10 points within 3 months of CPAP use. These findings highlight the importance of collaboration between mental health and sleep medicine professionals and opportunity for further study in this area. [Journal of Psychosocial Nursing and Mental Health Services, xx(xx), xx-xx.].