The present study aims to determine the effect of feeding system for Iberian pigs during the fattening period on tissue fatty-acid composition and rheological properties. Twenty-four Iberian barrows of the same age with an average initial liveweight of 100.2 kg were randomly distributed into three groups of eight pigs each. One group was fed under free-range conditions for 117 d. The other two groups were fed in confinement either with acorns from Quercus rotundifolia or a concentrate diet. Differences on subcutaneous backfat fatty-acid composition were found among feeding systems with the outer layer of backfat in concentrate-fed pigs containing more SFA and total n-6 and less MUFA, directly reflecting dietary fatty-acid composition. The longissimus dorsi intramuscular neutral lipids (NL) of free-range pigs contained higher C18:1 n-9, MUFA and lower SFA proportions than those fed with acorns or the concentrate diet. The liver NL in pigs fed acorns in confinement contained higher C18:1 n-9, MUFA and lower SFA proportions than those fed a concentrate diet or in free-range. Subcutaneous fat from pigs fed the concentrate diet was higher in hardness than those fed acorns in confinement or in free-range, while adhesiveness was higher in pigs fed acorns in confinement than in the remaining groups of pigs.