Fatty acid esters of hydroxyl fatty acids (FAHFAs) are a new family of endogenous lipids that exert anti-inflammatory action. Among the various FAHFA isomers, the dietary source of oleic acid-hydroxy stearic acid (OAHSA) and its anti-inflammatory functions are poorly understood. This study investigated the composition of OAHSA isomers in dietary oils and the impact of 12-OAHSA on obesity-induced inflammation. Liquid chromatography with tandem mass spectrometry analysis revealed that various dietary oils, including fish oil, corn oil, palm oil, soybean oil, and olive oil, present a wide variation in OAHSA profiles and amounts. The highest amounts of total OAHSAs are present in olive oil including 12-OAHSA. Compared to vehicle-treated obese mice, administration of 12-OAHSA significantly improved glucose homeostasis, independent of body weight. 12-OAHSA-treated mice displayed significantly reduced accumulation of CD11c⁺ adipose tissue macrophages, and CD4⁺/CD8⁺ adipose tissue T lymphocytes. Concomitantly, the expression of pro-inflammatory cytokine genes and the nuclear factor kappa-light-chain-enhancer of activated B cells signaling pathway were significantly decreased in the 12-OAHSA-treated adipose tissue, while the expression of the anti-inflammatory gene Il10 was markedly increased. Moreover, in vitro cell culture experiments showed that 12-OAHSA significantly inhibited the lipopolysaccharides-induced inflammatory response in macrophages by suppressing the nuclear factor kappa-light-chain-enhancer of activated B cells signaling pathway. Collectively, these results indicated that 12-OAHSA, as a component of olive oil, mitigates obesity-induced insulin resistance by regulating AT inflammation. Therefore, 12-OAHSA could be used as a novel nutritional intervention against obesity-associated metabolic dysregulation.