Purpose of ReviewWomen are twice as likely to develop post-traumatic stress disorder (PTSD) compared to men after a traumatic experience. The purpose of this mini review was to explore recent research on biological contributors to this sex difference.Recent FindingsWe identified 51 studies published since 2019. Studies found that beyond the influence of sex on the prevalence and symptoms of PTSD, there is evidence for and against sex-based differences in genetic and epigenetic factors (n= 8), brain structure and function (n= 11), neuroendocrine and inflammatory responses (n= 5), and in the role of sleep on emotional memory processing (n= 1). Sex differences were also observed in recovery and during PTSD treatment (n= 16). Finally, there is emerging evidence of sex-differentiated risk for medical and psychiatric comorbidities in PTSD (n= 10).SummaryRapid advances are being made using integrated multidisciplinary approaches to understand why females are at a heightened risk for developing PTSD.