Background: Sexual assault often triggers posttraumatic stress disorder (PTSD), a potentially chronic severe mental disorder. Most guidelines recommend selective serotonin reuptake inhibitors (SSRIs) and trauma-focused psychotherapies as treatment options. Interpersonal Psychotherapy (IPT), adapted for PTSD (IPT-PTSD), focuses on interpersonal consequences of trauma rather than confronting the trauma itself. Studies have found IPT-PTSD efficaciously reduced PTSD symptoms with limited attrition. No efficacy trials have compared IPT-PTSD and SSRI. We hypothesized IPT would reduce PTSD, anxiety, and depressive symptoms more than sertraline among women with PTSD following a recent sexual assault. Objectives: To compare the efficacy of IPT-PTSD to SSRI sertraline in a 14-week randomized clinical trial for women with PTSD following a recent sexual assault. Methods: Seventy-four women with PTSD who had suffered sexual assault in the last six months were randomly assigned to 14 weeks of IPT-PTSD (n = 39) or sertraline (n = 35). Instruments assessed PTSD, anxiety, and depressive symptoms. This randomized clinical trial was conducted in São Paulo, Brazil, using the Clinician-Administered PTSD Scale-5 (CAPS-5) as the primary outcome measure. Results: Both treatments significantly reduced PTSD, anxiety, and depressive symptoms, without between-group outcome differences. CAPS-5 mean decreased from 42.5 (SD = 9.4) to 27.1 (SD = 15.9) with sertraline and from 42.6 (SD = 9.1) to 29.1 (SD = 15.5) with IPT-PTSD. Attrition was high in both arms (p = .40). Conclusions: This trial showed within-group improvements without differences between IPT-PTSD and sertraline treatment of PTSD. Our findings suggest that non-exposure-based psychotherapies may benefit patients with PTSD, although we did not directly compare these treatments to an exposure therapy. Brazilian Clinical Trials Registry RBR-3z474z.