Hypoglycosylated MUC1 is a tumor-associated protein that is expressed on over 80% of all human cancers. In our recent clinical trial, individuals at-risk for colonic adenocarcinoma received a prophylactic MUC1 cancer vaccine. Many individuals responded producing high titers of anti-MUC1 IgG antibodies with no detectable toxicity. TCR repertoire sequencing also revealed several differentially abundant T cell clones induced by the vaccine. This trial provided a rare source of human antibodies raised and affinity-matured in a healthy human host to abnormal MUC1. We isolated and identified 13 anti-MUC1 monoclonal antibodies that could bind to several different epitopes on the MUC1 vaccine peptide with a range of affinities. They also stain MUC1 on human cancer cell lines and colon, breast, lung, and pancreas adenocarcinoma tissue sections while showing no reactivity against a large panel of normal tissues. We found that two of the antibodies are capable of performing MUC1-depdendent complement-mediated cytotoxicity (CDC). Next, we constructed a series of lentiviral vectors encoding chimeric antigen receptors (CARs) using scFv’s of the antibodies as antigen binding regions. Several CARs were able to retarget human primary T cells to become activated and produce cytokines in a MUC1-dependent manner, and were able to mediate lysis of MUC1+ human tumor cell lines. Preclinical testing in MUC1.tg mouse tumor graft model is underway. Being of fully human origin and showing a high-degree of tumor specificity and efficacy in preclinical experiments this research has the potential to enable clinical trials needed for approval of these reagents for cancer therapy.