Altered fatty acid (FA) composition is related to insulin resistance and CVD. One possible mediator may be inflammation, but longitudinal data relating FA composition to inflammation taking insulin resistance into account are limited. We investigated the long-term association between FA composition and C-reactive protein (CRP) concentrations in a large population-based cohort study in 767 men followed for 20 years. The association between FA composition in serum cholesteryl esters at age 50 and CRP concentrations at age 70 was investigated using linear regression. In addition, desaturase activities (stearoyl-CoA desaturase-1 (SCD-1), Δ5- and Δ6-desaturase) were estimated using FA product-to-precursor ratios. Insulin resistance was measured directly at follow-up by euglycaemic clamp. After adjusting for confounders (smoking, physical activity, alcohol intake, obesity and erythrocyte sedimentation rate) CRP concentrations were inversely associated with the proportion of 18 : 2n-6 (P = 0·002) and positively associated with 16 : 1n-7 (P = 0·008), 18 : 1n-9 (P = 0·0003), 20 : 5n-3 (P = 0·04) and estimated SCD-1 (P = 0·005) and Δ6-desaturase (P = 0·02) activities. After adding insulin resistance to the model, 18 : 1n-9, 18 : 2n-6 and SCD-1 remained significant predictors of CRP. A FA composition indicating low intake of 18 : 2n-6, high intake of SFA and high SCD-1 activity is, in a Swedish population of middle-aged men, associated with CRP concentrations 20 years later, even independently of obesity and insulin resistance.