No T cell receptor (TCR) T cell therapies have obtained clinical approval. The lack of strategies capable of selecting and recovering potent T cell candidates may be a contributor to this. Existing protocols for selecting TCR T cell clones for cell therapies such as peptide-MHC multimer methods have provided effective measurements on TCR affinities. However, these methods lack the ability to measure the collective strength of intercellular interactions (i.e., cellular avidity) and markers of T cell activation such as immunological synapse formation. This study describes a novel microfluidic fluid shear stress-based approach to identify and recover highly potent T cell clones based on the cellular avidity between living T cells and tumor cells. Our approach is capable of probing approximately up to 10,000 T cell-tumor cell interactions per run and can discriminate and recover highly potent T cells with up to 100% purity from mixed populations of T cells within 30 minutes. Markers of cytotoxicity, activation and binding avidity persisted when recovered high cellular avidity T cells were subsequently exposed to fresh tumor cells. These results demonstrate how microfluidic probing of cellular avidity may fast track the therapeutic T cell selection process and move us closer to precision cancer immunotherapy. This article is protected by copyright. All rights reserved.