Metabolic dysfunction-associated steatotic liver disease (MASLD) is one of the major public health challenges, with its prevalence increasing with age. Physiological changes associated with aging, such as reduced liver function, elevated oxidative stress, and impaired lipid metabolism, contribute to the development of this disorder. Evidence suggests that regular physical activity and the use of antioxidant supplements can play a significant role in prevention and management of MASLD. The present study aimed to investigate the effect of an eight-week moderate-intensity swimming program combined with a silymarin and vitamin C supplementation on the expression of genes related to cellular stress (BIP and CHOP), mitochondrial function (Cox18 and Oxa1), and tissue fibrosis marker (Col3A1) in aged male Wistar rats with MASLD. Twenty-five rats (14–16 months old) were randomly divided into five groups: healthy control, diseased control, swimming, supplement, and swimming + supplement. The swimming protocol was performed five sessions per week for eight weeks (30–60 minutes per session, 60–70% of maximal capacity), while the combined supplement (100 mg/kg silymarin and 500 mg/kg vitamin C) was administered daily by gavage. Gene expression was assessed using Real-Time PCR, and Col3A1 concentration was measured by ELISA. Results showed that swimming combined with supplementation significantly reduced BIP and CHOP expression, increased Cox18 and Oxa1 expression, and decreased Col3A1 levels compared to the diseased group. Therefore, the combined intervention of regular exercise and antioxidant supplementation may serve as an effective non-pharmacological strategy to reduce cellular stress, improve mitochondrial function, and prevent hepatic fibrosis during aging.