e21552 Background: Despite high rates of breast cancer (BC) in young Mexican women, information about their particular needs and concerns is largely unknown. Understanding the patients individual needs in a population with unique socio-cultural features is essential to guide supportive care and improve their quality of life. We aim to describe the unmet needs of Mexican young women with breast cancer (YWBC). Methods: A cross-sectional study including women with stage I-III BC aged 40 years or younger at diagnosis was conducted at the National Cancer Institute in Mexico City. YWBC were invited to complete the Supportive Care Needs Survey, Short Form-34 (SCNS-SF34), a comprehensive tool that measures the perceived unmet needs of cancer patients. The survey was previously adapted and validated in our population for its use. Results: 81 consecutive patients with median age at diagnosis of 35.09 (SD 3.9) years were included. 45.7% were married and 29.2% completed secondary school. 92.6% had stage II-III BC. 70.4% were undergoing active treatment and 29.6% were either on hormonal therapy or surveillance. From a total standardized score of 100, the health systems and information domain had the highest mean score (39.3), followed by the psychological domain (36.3). The sexuality domain had the lowest mean score (27). The highest ranked items of unmet needs (by mean crude score) were: to be informed about cancer is under control or diminishing (2.9), to be informed about things you can do to help yourself get well (2.8), lack of energy and fatigue (2.7), and fear about the cancer spreading (2.7). Perceived needs among patients undergoing active treatment were greater compared to those in follow-up (z = -2.390 p = 0.017), predominantly in the sexuality domain (z = -2.084 p = 0.037). Conclusions: Mexican YWBC have specific needs that are currently not systematically addressed. The predominant unmet need regarding health systems and information should be a priority. Further research to understand the needs and concerns of this unique and understudied patient population will aid tailor clinical interventions and supportive care.