Objectives: This study aimed to assess the unmet supportive care needs of Omani women with breast cancer (BC). Methods: This cross-sectional study was conducted from November 2020 to February 2021 among 250 adult Omani women diagnosed with BC at a university teaching hospital in Muscat, Oman. An Arabic version of the 34-item Supportive Care Needs Survey-Short Form tool was used to determine perceived unmet supportive care needs across five domains. Results: A total of 181 women participated in the study (response rate: 72.4%). The domain with the highest mean score per item was health system and information (mean score: 3.33), with the greatest unmet need in this domain being informed about things that the patient could do to help themselves get well (40.9%). The domain with the second highest mean score per item was patient care and support (mean score: 3.04), with the greatest unmet need being for clinicians to be more sincere with the patient (36.5%). Higher total mean scores were reported by women who had visited the hospital four times or more over the past two months (P = 0.045), those with stage 3 or 4 cancer (P = 0.047) and those who had recently undergone radiotherapy or chemotherapy (P = 0.014). Conclusion: Most unmet supportive care needs fell under the health system and information domain. Healthcare providers in Oman should explore patient concerns and provide sufficient information at various stages of the care process in order to decrease the anxiety associated with living with cancer. Keywords: Breast Neoplasms; Needs Assessment; Supportive Care; Women; Oman.