Metastasis is the major cause of breast cancer mortality, with angiogenesis and tumor-released exosomes playing key roles. However, the communication between breast cancer cells and endothelial cells and its role in tumor metastasis remains unclear. Here, we characterize a long noncoding RNA, RPPH1, which is upregulated in breast cancer tissues and positively associated with poor prognosis. Hypoxia microenvironment upregulates the expression of RPPH1 in breast cancer cells, and promotes its packaging into exosomes through hnRNPA1, leading to the maintenance of stemness and aggressive traits in cancer cells and angiogenesis in endothelial cells. The function of cellular and exosomal RPPH1 was confirmed in the MMTV-PyMT mouse model, in which ASO-RPPH1 therapy effectively inhibited tumor progression and metastasis. Mechanistically, RPPH1 protects IGF2BP2 from ubiquitination-induced degradation, stabilizes N6-methyladenosine (m6A)-modified FGFR2 mRNA, and activates the PI3K/AKT pathway. Our research unveils the role of RPPH1 in breast cancer metastasis and highlights its potential as a therapeutic target.