This randomized control trial aimed to evaluate the effect of health literacy intervention on self-management among older women with breast cancer undergoing chemotherapy. The study sample composed of 100 older breast cancer patients undergoing chemotherapy, randomly assigned into two groups. The study group (n=50) received six sessions every two weeks and the control group (n=50) received no intervention. Four tools were used; interview questionnaire, All Aspects of Health Literacy Scale, Patients' Self-Management Knowledge, and Chemotherapy Self-Management Scale. Chi-square test, independent samples t-test, paired t-test, and Pearson correlation were used for data analysis. The study findings showed statistically significant improvements in the study group’s health literacy, self-management knowledge, and self-management behaviors compared to the control group (p < .01). Health literacy intervention was effective and could be used to enhance patients’ health literacy, self-management knowledge, and self-management behaviors in older women with breast cancer undergoing chemotherapy.