Eicosatrienoic acid (Δ11,14,17-20:3; ETrA) is a rare naturally occurring n-3 polyunsaturated fatty acid (PUFA). Using murine RAW264.7 cells, the objectives were to determine how ETrA modulated phospholipid fatty acid compositions and the production of pro-inflammatory mediators. Incubation cells with ETrA dose-dependently increased the proportions of phospholipid ETrA and its metabolites to 33 % of the fatty acid total. Incorporation of ETrA also reduced the proportions of total n-6 PUFA and monounsaturated fatty acids (MUFA) by 30 and 60 %, respectively. ETrA suppressed LPS-stimulated nuclear factor-kappa B (NF-κB)-mediated nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression. However, no such suppressive effect on the production of prostaglandin E2 (PGE2), cytokines, or expression of cyclooxygenase-2 (COX-2) was observed. As compared with ETrA, eicosapentaenoic acid (EPA) exerted a more potent anti-inflammatory effect. In conclusion, although ETrA suppresses significant NO synthesis and iNOS expression, this n-3 PUFA was a less potent anti-inflammatory agent than EPA.