The present study tested a hypothesis that dietary fish oil (eicosapentaenoic acid+docosahexaenoic acid) in a commonly achievable dose ameliorates a systemic inflammation in pigs. Two groups of pigs of 16 animals each were fed a diet with either 2.5% of fish oil (F) or a control diet with 2.5% of palm oil (P). After 70 days of fattening, eight F and eight P pigs were challenged (F+; P+) i.v. by lipopolysaccharide. After 3 h, all pigs were sacrificed and blood, liver and visceral adipose tissue (VAT) samples were taken. No significant effect (P>0.05) of dietary oil on the feed intake and daily weight gain was found out. Less neutrophils (16.8% v. 28.8%; P<0.05) were found in the F+-leukocytes of the peripheral blood; F+ pigs had lower (P<0.05) percentage of the swine leukocyte antigen-D-related CD163+ (SLA-DR+ CD163+) macrophages in the VAT (15.4% v. 21.8%) and lower expression of the SLA-DR-CD163+ surface molecules of the VAT macrophages. No difference (P>0.05) between F+ and P+ pigs in the peroxisome proliferator-activated receptor γ, GPR120, Adipor1 and Adipor2 (adiponectin receptor) gene expression, respectively, was established; plasma adiponectin was the same (21.1 ng/ml) in F+ and P+ pigs. In comparison with the P+ pigs, increased expression of the lipopolysaccharide-binding protein (LBP) gene and intercellular adhesion molecule 1 (ICAM1) gene was found out in the liver of the F+ pigs; expression of the tumor necrosis factor α (TNFα) gene was higher in the liver but lower in the VAT of the F+ pigs (P<0.05). The F+ pigs had higher (P<0.05) plasma concentration of both anti-inflammatory cytokine interleukin-4 (0.46 v. 0.04 ng/ml) and pro-inflammatory TNF-α (13.41 v. 7.72 ng/ml). It was concluded that dietary fish oil at the tested amount had a negligible effect on expression of the evaluated receptor genes and plasma adiponectin, and had an ambiguous effect on expression of cytokine genes and plasma cytokine levels.