The aim of the present 12-week, open-label study was to investigate the effect of olanzapine augmentation in outpatients with depression with melancholic features who demonstrated partial response to standard antidepressants but who were reluctant to change antidepressants. The subjects consisted of 22 outpatients meeting the DSM-IV-TR criteria for major depression. Olanzapine was initially added at 2.5 mg/day and the dose was adjusted according to the clinical condition. Data were analyzed using an intention-to-treat methodology. A paired t-test was used to compare total Montgomery Asberg Depression Rating Scale (MADRS) scores before treatment, at baseline (prior to olanzapine), and 4, 8, and 12 weeks after starting olanzapine. Of 22 enrolled patients, 20 completed the trial. The mean (±SD) MADRS score was 17.1 ± 1.0 at baseline and decreased significantly to 8.1 ± 3.2 at 4 weeks after the administration of olanzapine. This significant reduction continued until 12 weeks, when the mean MADRS score was 4.9 ± 2.9, indicating full remission. These results suggest that olanzapine augmentation may be useful for patients with depression in partial remission. A controlled, double-blind trial, however, is needed to confirm these preliminary findings.