The purpose of this study was to examine the possible additive neurocognitive deficits in adults with both attention-deficit/hyperactivity disorder (ADHD) and serious depressive symptoms. Participants were 54 university students who completed a psycho-educational assessment. Three groups were examined: a group with comorbid ADHD and elevated depressive symptoms (ADHD + DEP; N = 18); a group with ADHD only (N = 18); and a group with elevated depressive symptoms only (DEP; N = 18). Group differences were examined on a battery of neurocognitive tests. The ADHD + DEP group performed significantly worse than the other groups on processing speed tasks and delayed recall of conceptual verbal information and significantly worse than the ADHD group on shifting tasks. Depressive symptom severity was significantly correlated with processing speed, verbal memory performance, and shifting in the ADHD and ADHD + DEP groups. Results suggest that the co-occurrence of ADHD and depressive symptoms in adults is associated with additional neurocognitive impairment.