Abstract <p>To evaluate the effect of seed priming with chitosan on the physiological and biochemical characteristics of pea seedlings under the influence of accelerated aging, a factorial experiment in the form of a completely randomized design with three replications was conducted at the University of Mohaghegh Ardabili, Iran in 2024. The treatments included four aging levels (0, 15, 20, and 25 days) and four chitosan levels (0, 0.1, 0.2, and 0.5% w/v, all dissolved in 1% acetic acid). The results showed that aging decreased germination percentage, plumule length, seedling length, plumule FW, radicle DW and seedling length vigor index. However, priming with different levels of chitosan, especially 0.5%, improved these characteristics compared to the control. Amylase enzyme activity and protein content in chitosan treatment showed an increase of about 35 and 34%, respectively compared to the control. The activity of catalase and peroxidase enzymes, content of proline and soluble sugars increased by about 77, 96, 71, and 53%, respectively, in pretreatment with 0.5% chitosan and 25 days of aging compared to the control. The highest amount of malondialdehyde was obtained in hydro (control) and 25 day aging. The results showed that seed pretreatment with 0.5% chitosan can be considered as an effective way to improve the physiological and biochemical traits of pea seeds and can reduce the deleterious effects of aging on some traits in pea seedlings.</p>