The design of specific protein binders is a core-goal of biologics design. However, current techniques rely on medium-throughput, laborious, well-by-well screening, or standard phage, yeast, or mRNA display, which screen binders in non-human contexts. To create a human cell-based binder screening platform, here, we developed a high-throughput screening approach based on genetically engineering chimeric antigen receptors (CAR)-expressing cells with libraries of binding proteins, and co-culturing them with target-expressing cells. Using an NFAT-inducible GFP reporter to monitor CAR activation, we establish a novel platform to screen experimentally and artificial intelligence-generated binders toward diverse target substrates on the surface of human cells for downstream therapeutics development.