Nutrition plays a minor role in psychiatric practice which is currently dominated by a pharmacological treatment algorithm. An accumulating body of evidence has implicated deficits in the dietary essential long-chain omega-3 (LC. n-3) fatty acids, eicosapenaenoic acid (EPA) and docosahexaenoic acid (DHA), in the pathophysiology of several major psychiatric disorders. LC. n-3 fatty acids have an established long-term safety record in the general population, and existing evidence suggests that increasing LC. n-3 fatty acid status may reduce the risk for cardiovascular disease morbidity and mortality. LC. n-3 fatty acid supplementation has been shown to augment the therapeutic efficacy of antidepressant, mood-stabilizer, and second generation antipsychotic medications, and may additionally mitigate adverse cardiometabolic side-effects. Preliminary evidence also suggests that LC. n-3 fatty acid supplementation may be efficacious as monotherapy for primary and early secondary prevention and for perinatal symptoms. The overall cost-benefit ratio endorses the incorporation of LC. n-3 fatty acids into psychiatric treatment algorithms. The recent availability of laboratory facilities that specialize in determining blood LC. n-3 fatty acid status and emerging evidence-based consensus guidelines regarding safe and efficacious LC. n-3 fatty acid dose ranges provide the infrastructure necessary for implementation. This article outlines the rationale for incorporating LC. n-3 fatty acid treatment into psychiatric practice. © 2013 Elsevier B.V.