Placental inflammation is associated with several pregnancy disorders. Inflammation is limited by anti-inflammatory and pro-resolving mechanisms, the latter in part mediated by resolvins and protectins derived from omega-3 (n-3) polyunsaturated fatty acids (PUFAs). We have recently reported that maternal dietary supplementation with n-3 PUFAs enhanced placental and fetal growth in the rat, and was associated with reduced oxidative damage as measured by F₂-isoprostanes. Here we examine effects of dietary n-3 PUFAs on levels of resolvins, protectins and their precursors, and expression of the lipoxygenase (LOX) enzymes involved in their production, in the rat placental labyrinth zone. Rats were fed either standard (Std) or high n-3 PUFA (Hn3) diets from day 1 of pregnancy, and tissues collected on days 17 or 22 (term = day 23). Maternal Hn3 diet increased levels of resolvin and protectin precursors, 18R/S-HEPE (12 to 54-fold; P<0.001) and 17R/S-HDHA (1.5 to 2.3-fold; P<0.01) at both gestational stages. Resolvins 17R-RvD1 and RvD1 were increased by Hn3 diet at day 22 (4.7 and 6.7-fold respectively; both P<0.001), coincident with higher Lox15b and Lox5 mRNA expression, while levels of RvD2 were increased at both days (2.1 and 2.7-fold at days 17 and 22 respectively; P<0.05). The protectins, PD1 (5.4-fold; P<0.001) and 10S,17S-DiHDHA (11-fold; P<0.001), increased over late gestation coincident with higher Lox15a mRNA expression (P<0.001), and further increased with Hn3 diet (1.5 to 2.2-fold and 2.1 to 3.4-fold respectively; P<0.05). Overall, our data indicate that maternal n-3 PUFA supplementation enhances expression of enzymes in the n-3 PUFA metabolic pathway, and increases placental levels of resolvins and protectins.