Abstract Waldenström macroglobulinemia (WM) is a rare, lymphoplasmacytic lymphoma characterized by hypersecretion of immunoglobulin M (IgM) protein and tumor infiltration into the bone marrow and lymphatic tissue. Our understanding of the mechanisms driving the development and progression of WM is currently by the shortage of representative cell models available for study. We describe here the establishment of a new WM cell line, MWCL-1. Comprehensive genetic analyses have unequivocally confirmed a clonal relationship between this novel cell line and the founding tumor. MWCL-1 cells exhibit an immunophenotype consistent with a diverse, tumor clone composed of both small B lymphocytes and larger lymphoplasmacytic cells and plasma cells: CD3−, CD19+, CD20+, CD27+, CD38+, CD49D+, CD138+, cIgM+, and κ+. Cytogenetic studies identified a monoallelic deletion of 17p13 (TP53) in both the cell line and the primary tumor. Direct DNA resequencing of the remaining copy of TP53 revealed a missense mutation at exon 5 (V143A, GTG>GCG). In accordance with primary WM tumors, MWCL-1 cells retain the ability to secrete high amounts of IgM protein in the absence of an external stimulus. The genetic, immunophenotypic, and biologic data presented here confirm the validity of the MWCL-1 cell line as a representative model of WM.