CAR (chimeric Antigen Receptor) T cells represent a promising immunotherapy approach to treat cancer by redirecting the immune system to attack cancer cells. On the other hand, tumor cells have developed strategies to evade the immune system by overexpressing ligands that, upon binding to the corresponding immune checkpoint receptors on CAR T cells, impair their killing activity and promote their exhaustion. Immune checkpoint blockers have shown promise in inhibiting this interaction, thus mitigating the immunosuppressive effects and improving CAR T cell performance. However, the occurrence of severe immune-related side effects due to their systemic activity, and the adaptation of the tumor microenvironment that can eventually lead to resistance, are still unresolved. We have devised a strategy to render CAR T cells devoid of two major immune checkpoints via hit-and-run epigenome editing. Delivering mRNA encoding for designer epigenome modifiers (DEMs) targeting PDCD1 or LAG3, the deposition of de novo cytosine methylation in their promoters sustainably silenced the expression of the two genes both in primary T cells and in CAR T cells directed against the prostate-specific membrane antigen (PSMA). Importantly, silencing was stable upon multiple exposure of the CAR T cells to specific activation signals. Furthermore, the epigenetically edited CAR T cells were functionally indistinguishable from their parental unmodified cells in an array of in vitro assays, demonstrating the safety of epigenome editing in CAR T cells. Our results propose this technology as a novel approach to modulate T cells inhibitory pathways in a targeted manner needless of DNA sequence modification.