The purpose of this article is to review the current literature regarding the role of omega-3 (ω-3) fatty acids (mainly eicosapentaenoic acid and docosahexaenoic acid) in the etiology and treatment of psychiatric disorders. Omega-3 fatty acids are essential for normal structure and function of neuronal membranes. They also influence cell signaling and are precursors to the eicosanoids, which play important regulatory roles in a wide range of physiological functions. There has been considerable interest in the potential use of ω-3 fatty acids for the treatment of psychiatric disorders including depression, bipolar disorder, schizophrenia, borderline disorder, obsessive compulsive disorder and childhood developmental and psychiatric disorders. This article provides a critical review of the recent findings and discusses future directions and questions that remain unanswered.