Purpose: Newer drugs incorporated in prophylactic regimens for chemotherapy-induced nausea and vomiting (CINV) have resulted in significantly reduced rates of this feared complication of cytotoxic chemotherapy. However, both delayed chemotherapy-induced nausea and breakthrough CINV remain difficult areas of management and require novel treatment strategies. Recent randomized trial evidence has suggested that olanzapine, an atypical antipsychotic, may have a role in both the prevention and treatment of CINV. A systematic review was conducted to assess the efficacy of olanzapine in (a) preventing CINV in highly emetogenic chemotherapy (HEC) and moderately emetogenic chemotherapy (MEC) and (b) the treatment of breakthrough CINV. The toxicity of olanzapine in this setting was also reviewed. Methods: MEDLINE, Embase and Cochrane Database of Systematic Reviews databases were searched to identify all randomized clinical trials (RCTs) investigating olanzapine in patients receiving chemotherapy. Results: A total of 488 patients from three trials of CINV prophylaxis and 323 patients from three trials of breakthrough CINV were included. Regimens including olanzapine were associated with significant improvements in CINV prevention with both HEC and MEC. Single agent olanzapine for breakthrough nausea was superior to standard alternative options. Conclusion: Data from RCTs support the use of an olanzapine containing combination regimen as an option for CINV prophylaxis and single agent olanzapine for the treatment of breakthrough CINV. In the included trials, the short duration of olanzapine appears safe and well tolerated.