This clinical practice guideline update provides recommendations for treating breakthrough chemotherapy‐induced nausea and vomiting (CINV) and preventing refractory CINV in pediatric patients. Two systematic reviews of randomized controlled trials in adult and pediatric patients informed the recommendations. In patients with breakthrough CINV, escalation of antiemetic agents to those recommended for chemotherapy of the next higher level of emetogenic risk is strongly recommended. A similar recommendation to escalate therapy is made to prevent refractory CINV in patients who did not experience complete breakthrough CINV control and are receiving minimally or low emetogenic chemotherapy. A strong recommendation to use antiemetic agents that controlled breakthrough CINV for the prevention of refractory CINV is also made.