Chimeric antigen receptor Tcells (CART) targeting lymphocyte antigens can induce Tcell fratricide and require additional engineering to mitigate self-damage. We demonstrate that the expression of a chimeric antigen receptor (CAR) targeting CD5, a prominent pan-T cell antigen, induces rapid internalization and complete loss of the CD5 protein on Tcells, protecting them from self-targeting. Notably, exposure of healthy and malignant Tcells to CD5.CART cells induces similar internalization of CD5 on target cells, transiently shielding them from cytotoxicity. However, this protection is short-lived, as sustained activity of CD5.CART cells in patients with Tcell malignancies results in full ablation of CD5+ Tcells while sparing healthy Tcells naturally lacking CD5. These results indicate that continuous downmodulation of the target antigen in CD5.CART cells produces effective fratricide resistance without undermining their on-target cytotoxicity.