Fatty acids and other components of the diet may modulate, among others, mechanisms involved in homeostasis, aging, and age-related diseases. Using a proteomic approach, we have studied how dietary oil affected plasma proteins in young (6 months) or old (24 months) rats fed lifelong with two experimental diets enriched in either sunflower or virgin olive oil. After the depletion of the most abundant proteins, levels of less abundant proteins were studied using two-dimensional electrophoresis and mass spectrometry. Our results showed that compared with the sunflower oil diet, the virgin olive oil diet induced significant decreases of plasma levels of acute phase proteins such as inter-alpha inhibitor H4P heavy chain (at 6 months), hemopexin precursor (at 6 and 24 months), preprohaptoglobin precursor (at 6 and 24 months), and α-2-HS glycoprotein (at 6 and 24 months); antioxidant proteins such as type II peroxiredoxin (at 24 months); proteins related with coagulation such as fibrinogen γ-chain precursor (at 24 months), T-kininogen 1 precursor (at 6 and 24 months), and apolipoprotein H (at 6 and 24 months); or with lipid metabolism and transport such as apolipoprotein E (at 6 and 24 months) and apolipoprotein A-IV (at 24 months). The same diet increased the levels of apolipoprotein A-1 (at 6 and 24 months), diminishing in general the changes that occurred with age. Our unbiased analysis reinforces the beneficial role of a diet rich in virgin olive oil compared with a diet rich in sunflower oil, modulating inflammation, homeostasis, oxidative stress, and cardiovascular risk during aging. ; This work was supported by a Proyectos Internacionales Grant from Junta de Andalucía to JMV, a Proyectos de Excelencia Grant (P09-CVI-4887) from Junta de Andalucía to JMV, BIO-276 Grants from Junta de Andalucía and the University of Córdoba to JMVM, and a Proyectos de Excelencia Grant (AGR-922) from Junta de Andalucía) to FPJ. MS was funded by AGR922 and BIO-276 Grants. ; Peer Reviewed