This study describes chemotherapy-induced nausea and vomiting (CINV) control rates in pediatric and adult patients who did or did not receive guideline-consistent CINV prophylaxis. We conducted a systematic literature review of studies published in 2000 or later that evaluated CINV control in patients receiving guideline-consistent vs. guideline-inconsistent CINV prophylaxis and reported at least one CINV-related patient outcome. Studies were excluded if the guideline evaluated was not publicly available or not developed by a professional organization. Over-prophylaxis was defined as antiemetic use recommended for a higher level of chemotherapy emetogenicity than a patient was receiving. We identified 7060 citations and retrieved 141 publications for full-text evaluation. Of these, 21 publications (14 prospective and seven retrospective studies) evaluating guidelines developed by six organizations were included. The terms used to describe CINV endpoints and definition of guideline-consistent CINV prophylaxis varied among studies. Included studies either did not address over-prophylaxis in their definition of guideline-consistent CINV prophylaxis (48%; 10/21) or defined it as guideline-inconsistent (38%; 8/21) or guideline-consistent (3/21; 14%). Eleven included studies (52%; 11/21) reported a clinically meaningful improvement in at least one CINV endpoint in patients receiving guideline-consistent CINV prophylaxis. Ten reported a statistically significant improvement. This evidence supports the use of guideline-consistent prophylaxis to optimize CINV control. Institutions caring for patients with cancer should systematically adapt CINV CPGs for local implementation and routinely evaluate CINV outcomes.