The aging brain undergoes modifications in its lipid composition and, especially, in plasmalogen (Pl) levels. These phospholipids are known to be reservoirs of polyunsaturated fatty acids and often considered as endogenous antioxidants. The objectives of this study were to quantify Pls and free aldehydes (products of Pl oxidation) in the rat brain after 21 months of age and to determine the impact of dietary α-linolenic acid (ALA) and docosahexaenoic acid (DHA) on these levels. Rats (21 months) from 2 generations of n-3–deficient animals were fed either a n-3 fatty acid–deficient diet—a diet containing ALA alone or with 0.6% of DHA. At 21 months and after 3 or 5 months of diet, Pl, free aldehyde, and DHA levels were assessed in the hippocampus, cortex, and cerebellum. Plasmalogen levels significantly decreased in the cortex and cerebellum of n-3–deficient 24-month-old rats. Dietary ALA and DHA at nutritional levels have the same efficiency to restore DHA levels in the brain of aged rat. Plasmalogen and free aldehyde levels were not significantly influenced by dietary n-3 fatty acids. Plasmalogens were not more oxidized when phospholipids were enriched in DHA, compared with the situation of n-3 fatty acid deficiency. In conclusion, during aging, Pl levels decrease in some structures of the brain. The evolution of aldehyde levels may not explain changes occurring during physiologic aging. Lastly, the bioequivalence of dietary ALA and DHA as sources of docosahexaenoate accretion could be similar in aged rat brain.