Background The efficacy, safety and tolerability of adjunctive armodafinil for cognitive performance, and negative and affective symptoms, were examined in 60 patients with schizophrenia or schizoaffective disorder. Method This was a 6-week, double-blind, placebo-controlled, fixed dose trial of armodafinil (150mg/d) augmentation in patients with clinically stable schizophrenia or schizoaffective disorder. Cognition, psychopathology, alertness/wakefulness and adverse effects were assessed with standardized rating instruments. The primary endpoint was performance on measures of attention/vigilance. Results Patients were randomly allocated to adjunctive armodafinil or placebo. There was a significant Drug×Time interaction effect for attention/vigilance, due to modest non-significant worsening in the armodafinil group and improvement in the armodafinil group [CPT-Pairs d′, F(1,40)=6.2, p=0.017]. However, it became non-significant after correction for multiple comparisons. There were no differences between armodafinil and placebo in other cognitive domains or psychopathology measures. However, armodafinil was associated with significant improvement in the Scale for the Assessment of Negative Symptoms (SANS) anhedonia–asociality [F(1,41)=4.1, p=0.05]. Conclusions There were no significant differences in neurocognitive measures between adjunctive armodafinil and placebo in this 6-week study. Armodafinil improved anhedonia–asociality, but not other negative symptom domains.