A novel, easy to perform PCR-based method employing specific DNA methylation biomarkers to detect B-cell neoplasms in a variety of B-cell lines and B lymphoblastic leukemia (B-ALL) patient specimens has been developed. This method detects as few as 5 B-ALL cells, or 1 B-ALL cell in 1,000,000 normal background blood cells using a single marker, DLC-1 gene CpG island (CGI) methylation. By adding two additional markers PCDHGA12 and RPIB9, over 80% of B-ALL cases were detected in patients’ bone marrow and/or peripheral blood specimens. We have traced clinical B-ALL cases up to 10 years retrospectively and the DLC-1 methylation is correlated with patient clinical status. Thus, this epigenetic-based molecular method demonstrates its potential use in the diagnosis of B-cell neoplasia, in addition to traditional approach such as clinical features, morphology, immunophenotype, and genetic analysis.