Here we report on a novel biophotonic assay system for the detection and quantitation of chemotaxis, the directed movement of cells in response to chemokine concentration gradients. Our assay employs a firefly luciferase (ffLuc)-generated biophotonic signal to quantify cellular migration in 96-well microplate chemotaxis instruments. When compared to direct cell enumeration, the biophotonic reporter method is superior in accuracy, reproducibility, and sensitivity. As a proof-of-concept, we demonstrate the utility of this assay for quantifying the chemotactic response of ex vivo expanded ffLuc(+) primary human T-cells to recombinant human chemokines MCP-1, RANTES, and IP-10. The 96-well microplate format and in situ biophotonic detection of cells are amenable to high-throughput screening of peptides and small molecule libraries to identify agonists and antagonists of cellular chemotaxis, to analyze biological fluids for chemotactic activity, and to study chemotaxis in a variety of cell types.