Purpose <p>Interleukin 1 receptor-associated kinase 1, 4 (IRAK 1/4) inhibitor exerts anti-inflammatory and immuno-modulatory effects; however, its role in high-fat diet-induced vascular dysfunction and cognitive impairment is not known, and therefore investigated in the present study. </p> Method &amp; Results <p>Animals were fed either a high-fat diet (60% Kcal fat) or a chow diet (10% Kcal fat) for 12 weeks to induce hyperlipidemia and weight gain. High-fat diet-fed animals were then treated with vehicle, IRAK1/4 inhibitor (2.2 mg/kg, i.p.) and a reference drug, Orlistat (20 mg/kg, oral gavage), for 4 additional weeks. Protein levels were assessed by ELISA or Western blotting, and mRNA by RT-PCR. IRAK1/4 inhibitor and reference drug, Orlistat treatment, prevented HFD-induced increase in body weight gain, fasting blood glucose and plasma lipids, improved discrimination between the familiar and the novel arm in the Y-Maze test, alleviated percent avoidance in two-way active avoidance, and freezing percent in contextual fear conditioning test. The treatments attenuated the levels of systemic inflammatory cytokines IL-1β, CRP, as well as TNF-α, IL-6 and protein expression of Iba-1, GFAP, HIF-1α, and restored the BDNF levels in the pre-frontal cortex of HFD-fed treated mice. IRAK 1/4 inhibitor exerted these effects by blocking proteasomal degradation of IκB-α protein in the pre-frontal cortex of HFD-treated mice. In addition, the treatments prevented HFD-induced increase in vascular ICAM-1, VCAM-1, MCP-1, COX-1 and COX-2 mRNA expression, and restored vascular eNOS mRNA levels as well as the Acetylcholine (300 ρM-300 μM) induced relaxations of PE (1 µM) pre-contracted aortic rings. </p> Conclusion <p>IRAK1/4 inhibitor attenuates HFD-induced inflammation, vascular dysfunction and cognitive impairment in obese mice. </p>