Background/Aims: We compared the efficacy of the granisetron transdermal system (GTS) with that of ondansetron for controlling chemotherapy-induced nausea and vomiting (CINV) in patients treated with highly emetogenic chemotherapy (HEC). Methods: We randomized a total of 389 patients to groups treated by GTS and ondansetron before HEC. The primary endpoint was the percentage of patients achieving complete response (CR; no retching/vomiting/rescue medication) of CINV from the time of chemotherapy initiation to 24 hours after the last administration of chemotherapy (prespecified non-inferiority margin of 15%). Quality of life (QoL) was also assessed using the Functional Living Index-Emesis (FLIE). Results: The per protocol analysis included 152 (47.80%) and 166 patients (52.20%) in the GTS and ondansetron groups, respectively. In the full analysis set, the most common diagnosis, regimen, and period of chemotherapy were lung cancer (149 patients, 40.27%), cisplatin-based regimen (297 patients, 80.27%), and 1 day chemotherapy (221 patients, 59.73%). The CR rates were 86.84% and 90.36% in the GTS and ondansetron groups, respectively; the treatment difference was −3.52% (95% confidence interval, −10.52 to 3.48) and met the primary endpoint, indicating that GTS was not inferior to ondansetron. Patient satisfaction, assessed on the FLIE, showed significantly higher scores in the GTS group compared to the ondansetron group (mean ± standard deviation, 1,547.38 ± 306.00 and 1,494.07 ± 312.05 mm, respectively; p = 0.0449). Conclusions GTS provided effective, safe, and well-tolerated control of CINV and improved the QoL in HEC.