Hypercalcemia is a potentially life-threatening metabolic condition that commonly occurs in advanced malignancies, particularly solid tumors such as breast cancer. This condition often presents nonspecific symptoms like nausea, confusion, or polyuria in the emergency department, frequently leading to misdiagnosis and delayed treatment. In breast cancer, hypercalcemia is typically driven by paraneoplastic mechanisms, including parathyroid hormone-related peptide (PTHrP) secretion and osteolytic bone metastases, both of which disrupt calcium homeostasis. Furthermore, immune dysregulation or ectopic vitamin D production may also contribute to disease progression. This manuscript summarizes current evidence on the emergency presentation, diagnosis, and acute management of hypercalcemia in patients with breast cancer. It highlights key risk factors, including tumor subtypes, endocrine therapies, and changes in bone microenvironment, and outlines practical diagnostic approaches to facilitate early identification. Moreover, it compares therapeutic options, including intravenous hydration, calcitonin, bisphosphonates, and denosumab. Additionally, the review examines the prognostic significance of hypercalcemia, which often indicates disease progression and is associated with increased rates of intensive care unit (ICU) admissions and mortality. Overall, these insights aim to guide clinical decision-making and support future research efforts to establish standardized protocols and predictive models for breast cancer–associated hypercalcemia.