Bcl10 (B-cell CLL/lymphoma 10) is a 233 amino acid CARD (caspase recruitment domain)-containing cellular protein, increasingly recognized as a mediator of NFkappaB activation in non-immune, as well as immune cells. Due to the importance of Bcl10 in diverse cell types, we developed a solid-phase, enzyme-linked immunosorbent (ELISA) assay to precisely measure Bcl10 in small volume cell lysates, using recombinant Bcl10 to standardize the assay. Standard curve measures Bcl10 from 0.25 ng/mL to 16 ng/mL, with very low intra- and inter-assay variation. Sample dilution and exogenous Bcl10 recovery experiments, comparisons with Western blot, and linear response to increasing doses of known Bcl10 activators confirm the specificity and precision of the ELISA.