We developed cell-free DNA (cfDNA) methylation signatures for minimally invasive breast cancer detection, distinction, and estrogen receptor (ER) status classification with cell-free Methylated DNA Immunoprecipitation and Sequencing (cfMeDIP-seq). We profiled peripheral blood plasma from 87 patients with mBC spanning ER-positive/HER2-negative (ER+/HER2-), HER2-positive, and triple-negative breast cancer (TNBC).