This study aims to identify the effect of lavender aromatherapy intervention on the sleep quality of breast cancer patients. The research method used is quantitative with a randomized controlled trial design with a control group pretest-posttest design. The results showed a difference in the mean sleep quality in the intervention group and the control group after being given the intervention with a p-value of 0.005 (p < 0.05). In conclusion, lavender aromatherapy is recommended as an alternative therapy to improve the sleep quality of breast cancer patients.   Keywords: Lavender Aromatherapy, Breast Cancer, Sleep Quality