4-isopropyl-2,6-bis(1-phenylethyl)aniline 1 (KTH13-AD1) is a metabolite of Cordyceps bassiana that has been traditionally used to treat various inflammatory disease. Even though it has the magnificent pharmaceutical potential, there was not much understanding on its anti-inflammatory actions. Therefore, this study was aimed to determine the anti-inflammatory effects of KTH13-AD1. We found that KTH13-AD1 suppressed nitric oxide (NO) and reactive oxygen species (ROS) production in lipopolysaccharide (LPS)- or sodium nitroprusside (SNP)-treated macrophages (RAW264.7 cells). Similarly, mRNA expression of inducible NO synthase (iNOS) and tumor necrosis factor-a (TNF-a) analyzed by RT-PCR and real-time PCR was also reduced by this compound. Interestingly, KTH13-AD1 also strongly diminished the levels of NF-kB-mediated luciferase activities and nuclear translocated NF-kB family proteins. In agreement with these, KTH13-AD1 suppressed the upstream signaling pathway for NF-kB activation including IkBa, IKKa/b, AKT, p85/PI3K and Src in time- and dose-dependent manners. Therefore, these results strongly suggest that KTH13-AD1 has a strong anti-inflammatory activity via suppression of the NF-kB signaling pathway.