Most patients with non–small cell lung cancer (NSCLC) do not achieve durable clinical responses from immune checkpoint inhibitors, suggesting the existence of additional resistance mechanisms. Nicotinamide adenine dinucleotide (NAD)–induced cell death (NICD) of P2X7 receptor (P2X7R)–expressing T cells regulates immune homeostasis in inflamed tissues. This process is mediated by mono–adenosine 5′-diphosphate (ADP)–ribosyltransferases (ARTs). We found an association between membranous expression of ART1 on tumor cells and reduced CD8 T cell infiltration. Specifically, we observed a reduction in the P2X7R ⁺ CD8 T cell subset in human lung adenocarcinomas. In vitro, P2X7R ⁺ CD8 T cells were susceptible to ART1-mediated ADP-ribosylation and NICD, which was exacerbated upon blockade of the NAD ⁺ -degrading ADP-ribosyl cyclase CD38. Last, in murine NSCLC and melanoma models, we demonstrate that genetic and antibody-mediated ART1 inhibition slowed tumor growth in a CD8 T cell–dependent manner. This was associated with increased infiltration of activated P2X7R ⁺ CD8 T cells into tumors. In conclusion, we describe ART1-mediated NICD as a mechanism of immune resistance in NSCLC and provide preclinical evidence that antibody-mediated targeting of ART1 can improve tumor control, supporting pursuit of this approach in clinical studies.