Major depressive disorder (MDD) frequently co-occurs with posttraumatic stress disorder (PTSD), and this comorbidity is linked to reduced PTSD treatment response, yet moderators of outcomes for individuals with both conditions are unknown. This secondary analysis of a randomized clinical trial examined three depression-related moderators of treatment dropout and response among individuals with comorbid PTSD and MDD: single vs. multiple major depressive episodes (MDEs); current comorbid persistent depressive disorder (PDD); and relative diagnostic severity based on counts of clinically significant symptoms (PTSD vs. MDD). The sample consisted of active duty service members ( N = 94) with comorbid PTSD and MDD randomized to cognitive processing therapy (CPT) or CPT enhanced with behavioral activation (BA + CPT). PTSD and MDD symptoms were assessed at pretreatment, posttreatment, and 3-month follow-up. Participants with multiple MDEs were more likely to drop out of CPT compared to those with a single MDE ( p  = 0.013); dropout did not differ between these groups in BA + CPT ( p  = 0.23). Intent-to-treat multilevel models indicated MDEs were also associated with response, such that in BA + CPT, participants with multiple MDEs demonstrated greater PTSD ( p  = 0.028) and depression ( p  = 0.034) symptom reduction compared to participants with a single MDE. Relative diagnostic severity and comorbid PDD were not associated with dropout or response in the full sample ( p s  >  0.079) or within treatments ( p s  >  0.073). These preliminary results suggest that among service members with comorbid PTSD and MDD, those with recurrent depression may benefit from trauma-focused care augmented with BA to address depression.