Epitalon, also known as Epithalon or Epithalone, is a tetrapeptide, Ala-Glu-Asp-Gly (AEDG), which was synthesized based on the amino acids composition of Epithalamin, a bovine pineal gland extract, prior to its discovery in pineal gland polypeptide complex solution. During the last 25 years, this compound has been extensively studied using in vitro, in vivo, and in silico methods. The results of these studies indicate significant geroprotective and neuroendocrine effects of Epitalone, resulting from its antioxidant, neuro-protective, and antimutagenic effects, originating from both specific and nonspecific mechanisms. Although it has been demonstrated that Epitalon exerts, among other effects, a direct influence on melatonin synthesis, alters the mRNA levels of interleukin-2, modulates the mitogenic activity of murine thymocytes, and enhances the activity of various enzymes, including AChE, BuChE, and telomerase, it remains uncertain whether these are the sole mechanisms of action of this compound. Moreover, despite the considerable volume of research on the biological and pharmacodynamic characteristics of Epitalon, the quantity of physico-chemical and structural investigations of this peptide remains quite limited. This review aims to conclude the most important findings from such studies, thus presenting the current state of knowledge on Epitalon.