Inflammation and endoplasmic reticulum (ER) stress are associated with the development of insulin resistance and diabetes. Developmental endothelial locus-1 (DEL-1) enhances efferocytosis by macrophage and suppresses inflammatory response. However, effects of DEL-1 on ER stress-mediated insulin resistance in skeletal muscle remain unclear. Here, DEL-1 treatment augmented SIRT1 expression in C2C12 myocytes, thereby increasing SERCA2 expression in a dose-dependent fashion, and attenuated ER stress and insulin resistance under palmitate treatment condition. SIRT1/SERCA2 knockdown abrogated effects of DEL-1 on palmitate-induced insulin resistance as well as ER stress. Pharmacological significance of DEL-1 was confirmed by in vivo experiments. DEL-1 administration suppressed ER stress, insulin resistance, and SIRT1/SERCA2 expression in skeletal muscle of high-fat diet (HFD)-fed mice. Additionally, siRNA transfection-mediated in vivo downregulation of SIRT1 suppressed the effects of DEL-1 on expression of SERCA2, ER stress, and insulin resistance in skeletal muscle of HFD-fed mice. DEL-1 attenuates palmitate-induced and HFD-induced skeletal muscle ER stress and insulin resistance via SIRT1/SERCA2-mediated signaling.