Background: The prevalence of cancer increases year by year as well as the need of cancer therapy. Chemotherapy becomes the cancer modality therapy which is often used as the only option for an effective method. Mostly cancer patients are complaining about nausea as the side-effect of chemoterapy. Chemotherapy-induced nausea and vomiting (CINV) can be a bad impact for their quality of life, physical condition, and it can even change the patient’s obedience to the medication. The failure in handling CINV using antiemetic can cause the need for other therapy as a complementary and alternative therapy in handling CINV. Objective: To analyze the effect of peppermint aromatherapy on reduction of chemotherapy patient’s nausea scale in RSUD Panembahan Senopati Bantul. Methods: This research was pre-experiment with one group pra-post test design. The research sample consists of 15 respondents by purposive sampling technique. The measuring instrument in this research was Numeric Rating Scale (NRS). The data analysis used paired t-test with p value = < 0,05. Results: The result showed that mean of the nausea scale before giving peppermint aromatherapy was 7,3 and after giving peppermint aromatherapy is 3,7. The difference of mean value was 3,6 with p value=0,000 (p<0,05). Conclusion: There are significant effect of peppermint aromatherapy on reduction of chemotherapy patient’s nausea scale in RSUD Panembahan Senopati Bantul.