Thioredoxin 1 (Trx 1) is a redox-active small protein ubiquitously present in human body. It is one of the defensive proteins induced in response to various stress conditions. In addition to its anti-oxidative effect by dithiol-disulfide exchange in its active site, Trx 1 has anti-apoptotic and anti-inflammatory effects. Trx 1 overexpression has been shown to be effective in a wide variety of animal models for oxidative and inflammatory disorders. An administration of recombinant Trx 1 protein is also effective in animal models especially for severe acute lung diseases where Trx 1 is likely to act with its anti-inflammatory properties. Trx 1 in circulation shows anti-chemotactic effects for neutrophils and inhibitory effects against macrophage migration inhibitory factor (MIF). Neovascularization is also suppressed by Trx 1 via inhibition of the complement activation. Here we discuss precise mechanisms of Trx 1 and potential therapeutic approach of this molecule.