Ebselen, an organoselenium compound, mimics glutathione peroxidase activity. It is a multifunctional compound, which catalyzes several essential reactions for the protection of cellular components from oxidative and free radical damage. Based on a number of in vitro and in vivo studies, various mechanisms are proposed to understand the biomedical actions of ebselen in health and diseases. It modulates metallo-proteins, enzymatic cofactors, gene expression, epigenetics, antioxidant defenses and immune systems. Owing to these properties, ebselen is currently under clinical trials for the prevention and treatment of various disorders such as cardiovascular diseases, arthritis, stroke, atherosclerosis, and cancer. A few ebselen-based pharmaceutical agents are under extensive investigation. As ebselen has been shown to have significant cellular toxicity, appropriate studies are needed to redesign the ebselen-based therapy for clinical trials. This review summarizes current understanding of the biochemical and molecular properties, and pharmacological applications of ebselen and future directions in this area of research.