Objectives: The main goal of this study was to test the antiemetic effects of maropitant administered orally 2–2.5 h prior to morphine and dexmedetomidine in cats. Methods: Eighty-three healthy female cats were randomized to receive maropitant (8 mg orally; n = 39) or no treatment (control; n = 44), 2–2.5 h prior to morphine 0.1 mg/kg and dexmedetomidine 20 µg/kg intramuscularly. The incidence of sialorrhea, lip licking, retching and vomiting were recorded after morphine/dexmedetomidine injection. Results: There were no differences between groups in terms of age or weight. The treated group received a mean ± SD dose of maropitant of 2.9 ± 0.6 mg/kg. The incidence of sialorrhea and lip licking was no different between groups. The incidence of retching (control 36% vs maropitant 13%; P = 0.012) and emesis (control 32% vs maropitant 13%; P = 0.03) was significantly reduced in cats treated with maropitant. Conclusions and relevance: Maropitant 8 mg (total dose) administered orally 2–2.5 h prior to morphine and dexmedetomidine significantly reduced, but did not eliminate, the incidences of retching and vomiting. Maropitant did not decrease the occurrence of sialorrhea and lip licking, signs that may be indicative of nausea. Maropitant might be useful for morning administration to prevent emesis in outpatient cats requiring sedation or anesthesia; however, dose regimens or interval of administration might require improvement.