Porcine pancreatic enzymatic hydrolysates are rich in bioactive peptides and possess potential anti-aging properties, but their application and development are limited by the fishy odor of the raw material. In this study, flavor improvement through microbial fermentation was conducted, and the effects of fermented porcine pancreatic enzymatic hydrolysates on aging mice were investigated. A subacute aging mouse model was established via subcutaneous injection of D-galactose in the neck. Multi-tissue oxidative stress and inflammatory markers were assessed, and combined with pathological observations of the thymus, testes, and hippocampus, the intervention effects of fermented porcine pancreatic enzymatic hydrolysates on age-related tissue degenerative changes were explored. It was demonstrated that the characteristic fishy odor was improved by fermentation while bioactivity was retained, with the sensory score of the fermented sample increased from 4.30 to 15.90 points. In mouse serum and brain tissue, SOD activity was increased by 108.85% and 79.55%, and GSH levels were elevated by 59.24% and 63.29%, while MDA content was decreased by 55.09% and 28.25%, respectively, by high doses of the fermented product. Pro-inflammatory cytokine IL-6 and TNF-α levels were decreased by 58.01% and 41.19%, and 37.89% and 26.18%, respectively, and thymic fat infiltration, testicular seminiferous tubule atrophy, and hippocampal neuron loss were significantly improved. In conclusion, the fishy odor is removed and flavor is enhanced while the bioactivity of the enzymatic hydrolysates is preserved through fermentation. D-galactose-induced aging is delayed by this fermented product through antioxidant defense, inhibition of inflammatory responses, and multi-tissue protection, providing a theoretical foundation for its development as a functional food.