Immature O-glycosylation, characterized by the Tn antigen expression rather than complex glycans, is prevalent in advanced solid tumors and promotes immune evasion. We developed GlycoAvatars, magnetic beads coated with plasma-membrane glycoproteins from glycoengineered cancer cell models, to identify cancer-immune cell interactomes. Through proteomics, we propose uncovered numerous membrane and intracellular proteins involved in glycan-mediated immune signaling, providing a novel high-throughput strategy for identifying potential relevant molecular nodes foreseeing therapeutic targets.