Protein lipidation including cysteine palmitoylation (S-palmitoylation) significantly enhances protein hydrophobicity and membrane association. S-palmitoylation, catalyzed by the ZDHHC (zinc finger Asp-His-His-Cys) family of enzymes, occurs on a broad range of substrates. This modification regulates numerous biological pathways and cellular events, demonstrating significant relevance to various diseases. S-palmitoylation has been demonstrated to be critical for immune and inflammatory responses. However, understanding of the involvement of S-palmitoylation in antiviral immunity against RNA viruses remains very limited. RIG-I-like receptors (RLR) mediate innate immune signaling by detecting viral RNA and initiating the production of antiviral genes. In this study, we identified the S-palmitoylation of MAVS, a C-terminal tail-anchored protein on the mitochondrial outer membrane that functions downstream of RLR in antiviral signaling. We characterized ZDHHC7 as its palmitoyltransferase, modifying Cys508, a residue near the tail-anchor transmembrane helix. The transmembrane domain of tail-anchored proteins is usually sufficient for their sorting and maintaining correct localization. We are curious about the function of S-palmitoylation for tail-anchored proteins. Mechanistically, MAVS S-palmitoylation does not affect its localization at resting state. However, in response to viral challenges, MAVS S-palmitoylation stabilizes and promotes the aggregation of tail-anchored MAVS on the mitochondrial outer membrane, which provides important insights into how lipidation could affect tail-anchored or integral membrane proteins. Accordingly, ZDHHC7-mediated MAVS palmitoylation enhances antiviral response, and deletion of ZDHHC7 in mice increases susceptibility of the host to RNA virus infections, demonstrating a pro-inflammatory effect of ZDHHC7. The role of protein S-palmitoylation and how ZDHHCs are regulated under specific biological contexts needs to be further investigated. Furthermore, we found that treatment with the pan palmitoyl transferase inhibitor, 2-bromopalmitate, suppressed the development of systemic lupus erythematosus in a mouse model, suggesting that perturbation of lipid metabolism and protein lipidation could potentially benefit the treatment of autoimmune diseases. However, the underlying mechanisms of this effect require further exploration.