A cobalt(II) complex containing deprotonated mefenamic acid (Hmef) and imidazole (HIm), [Co(mef)(2)(HIm)(2)(CH3OH)(2)], has been synthesized and characterized by spectroscopic techniques (UV-vis, IR, and EPR), elemental analysis, and single-crystal X-ray diffraction analysis. The structure has distorted octahedral geometry around cobalt. The mefenamate is a monodentate ligand coordinated to the Co(II) through a carboxylate oxygen. This complex was tested as a catalyst for epoxidation of alkenes with tert-BuOOH in 1,2-dichloroethane solution. This catalyst was effective in epoxidation of various alkenes including non-activated terminal alkenes. The effects of solvent, oxidant, and temperature on the epoxidation of cyclohexene were investigated. In all cases, high yields of epoxidized alkenes were obtained.