Verbal learning and memory deficits are frequently reported in posttraumatic stress disorder (PTSD), but may be a product of its psychiatric comorbidities, especially major depressive disorder (MDD). To evaluate this hypothesis, 25 medication‐free patients with PTSD and comorbid MDD were compared to 148 medication‐free patients with equally severe MDD alone and to 96 nonpatients on a measure of verbal learning and memory. Additional measures of attention, working memory, and executive function were administered to evaluate their contribution to verbal memory impairment. Patients with comorbid PTSD and MDD demonstrated the greatest deficit in verbal learning compared to both MDD patients and nonpatients (omnibus effect sizes ranged d = 0.41 to 0.50), one that was not accounted for by other cognitive deficits. Findings suggest that a current diagnosis of PTSD makes a contribution to verbal learning deficits beyond the effect of depression alone.