Aging is characterized by immune decline, mainly due to thymic involution—the age-related shrinkage of the thymus gland. This leads to reduced T-cell production, chronic inflammation, and increased susceptibility to age-related diseases. Thymosin alpha-1 (Tα1), a peptide hormone produced by the thymus, exhibits potent immunomodulatory, anti-inflammatory, and antioxidant properties. It helps restore immune function by stimulating T-cell differentiation, enhancing thymic output, and modulating dendritic cell and macrophage activity. Preclinical and clinical studies show that Tα1 can improve vaccine response in the elderly and mitigate immunosenescence. The hybrid drug Refnot (a fusion of tumor necrosis factor alpha (TNFα) and Tα1) combines Tα1’s immunomodulation with TNF’s antitumor activity but has reduced toxicity. It represents a promising therapeutic approach to counteract age-related immune dysfunction and inflammation, potentially by slowing the aging process. Further research is needed to validate its long-term efficacy and safety in geriatrics.