Social support influences the development, severity, and evolution of posttraumatic stress disorder (PTSD). The objective of this systematic review was twofold: (1) to examine the role of social and marital support on the efficacy of cognitive–behavioral therapy (CBT) for PTSD and (2) to assess whether CBT for PTSD improves the quality of patients’ social and marital support. A systematic search of databases was executed and provided 17 eligible articles: 6 answering the 1st research question and 11 answering the 2nd research question. Most articles found that social and marital support play a role on the efficacy of CBT for PTSD. All but 1 article found that CBT for PTSD improved the quality of social and marital support. However, some studies included in this review were methodologically limited. More randomized clinical trials would then be needed to determine the specific and definite role of social and marital support pertaining to PTSD treatment.