BACKGROUND: Although breast cancer is the second leading cause of cancer-related mortality in women in the United States, few studies focus on the supportive care needs of patients living with metastatic breast cancer (MBC). OBJECTIVE: We studied quality of life (QOL), depression, anxiety, and prognostic understanding of patients with MBC. DESIGN: We conducted a cross-sectional study of 140 patients with MBC, stratified by receipt of endocrine therapy or chemotherapy. MEASUREMENTS: We evaluated anxiety and depression using the Hospital Anxiety and Depression Scale (HADS). We assessed QOL using the Functional Assessment of Cancer Therapy-Breast (FACT-B), specifically measuring the FACT-B Trial Outcome Index (TOI), which includes physical and functional well-being and breast cancer-specific symptoms. Higher FACT-B TOI scores represent better QOL. We used a 12-item questionnaire to assess patients' perceptions of their prognosis and goals of therapy. RESULTS: Compared to those taking endocrine therapy (n = 40), patients receiving chemotherapy (n = 100) reported lower scores on the FACT-B TOI (66.1 versus 72.5, p < 0.01) and more depression symptoms (HADS-D >7; 22% versus 7.5%, p = 0.03). Higher scores on the FACT-B TOI were associated with lower depression (β, -0.16; p < 0.01) and anxiety (β, -0.11; p < 0.01), and patients who reported frequent prognostic conversations with their oncologists had less depression (β, -1.28; p < 0.01). Thirty-nine percent (54/140) reported that their cancer was likely curable. CONCLUSION: Patients with MBC, particularly those treated with chemotherapy, may benefit from interventions to address their physical, functional, and breast cancer-related symptoms. Many do not report accurate prognostic understanding, and more frequent prognostic conversations might address this information gap.