Chitosan, a derivative of chitin, is a natural elicitor known for its biocompatibility, biodegradability and non-toxic properties, offering significant yet underexplored potential in advancing sustainable agriculture. Its application enhances plant physiological responses and mitigates the detrimental effects of both abiotic and biotic stresses across various growth stages. This study evaluated the effects of seed priming with chitosan and chitosan nanoparticles (CNPs) on the germination and seedling development of lentil (Lens culinaris L.). Seeds were primed with varying concentrations of chitosan (0.5 %, 1.0 %, 1.5 % and 2.0 %) and CNPs (50, 100, 150, 200 and 300 ppm). The priming duration was optimized for each treatment based on water uptake kinetics and initial radical emergence. Seed priming with a low concentration of chitosan (0.5 %) significantly improved seedling growth parameters, hydrolytic enzyme activities (amylase, protease), dehydrogenase and phytase activity, as well as yield-associated traits. In contrast, CNPs priming at 200 ppm showed superior enhancement across most laboratory and field parameters. Primed seeds treated with CNPs showed marked improvements, including a 12.6 % increase in germination potential, a 65.9 % increase in root length, a 97.4 % increase in shoot length, a 73 % increase in total seedling length, a 19.7 % rise in seedling dry weight and significant increases in vigor indices (94.8 % and 34.8 %) compared to non-primed seeds. Additionally, hydrolytic enzyme activities, including amylase, protease, dehydrogenase and phytase, were substantially elevated in primed seeds relative to untreated controls. To corroborate these findings, field experiments were conducted to assess the crop performance upon priming. Results revealed that seed priming with chitosan (0.5 %) and CNPs (200 ppm) significantly (P ≤ 0.05) enhanced seedling emergence, field establishment, plant height, pod and seed counts per plant, seed weight, overall yield and harvest index. These findings suggest that seed priming with 0.5 % chitosan or 200 ppm CNPs enhances seedling development, plant growth and yield by improving enzymatic activities and mobilization of food reserves.