Intimate partner violence (IPV) results in severe and chronic posttraumatic psychological symptoms, maladaptive trauma-related guilt (TRG) and functional impairment for many women. Cognitive Trauma Therapy (CTT) was developed to specifically address empirically identified contributors of distress and functioning difficulties specific to IPV and has been found to be efficacious in treating posttraumatic stress disorder (PTSD) and reducing TRG. The primary aim of this study was to investigate to what extent reductions in TRG contribute to improvements in PTSD and functioning, given evidence of the important role that TRG plays in posttraumatic distress in IPV survivors and the emphasis placed on TRG in CTT. Twenty women with IPV-related chronic and functionally impairing posttraumatic distress were recruited from the community and completed CTT as part of a larger neurobiological study of PTSD. Women experienced statistically and clinically significant improvements in functioning as well as expected reductions in PTSD and TRG with large effect sizes at post-treatment, and improvements were maintained at 3-month follow-up, with no participant meeting full PTSD criteria. Pre- to mid-treatment reductions in TRG predicted post-treatment PTSD and functioning outcomes. These findings support the efficacy of CTT and provide preliminary evidence for the importance of addressing TRG. Dismantling research is indicated to identify the active ingredient(s) of this multi-module treatment.