Chitosan is a promising natural biopolymer that stimulates growth, increases yield, and boosts-up plants' immune systems. A field experiment was conducted to study the effect of foliar application of chitosan on growth, yield and quality attributes (viz. chlorophyll-a, chlorophyll-b, total chlorophyll, carotenoids, total ash and major nutrient contents) of red amaranth. The field experiment was laid out in a Randomized Completely Block Design (RCBD) with three replications and six treatments [viz. T0 = Control (no chitosan application); T1 = 100 mg L-1; T2 = 150 mg L-1; T3 = 200 mg L-1; T4 = 250 mg L-1 and T5 = 300 mg L-1 chitosan solution]. The study results revealed that the application of chitosan at different doses had no significant effect on plant height, the number of leaves plant-1, and the moisture content of red amaranth. But there were significant variations in stem diameter, root length, and yield of red amaranth. Similarly, the application of chitosan at different doses also showed a significant effect on chlorophyll contents, carotenoids and total ash contents of red amaranth. The average chlorophyll-a, chlorophyll-b, total chlorophylls, carotenoids and ash content of red amaranth ranged from 6.02-9.51, 3.67-5.92 and 9.68-15.15 mg g-1 tissue, 0.20-0.28 µg g-1 sample (fresh wt.), and 16.36-17.69%, respectively. Among the major nutrient elements, the amount of Ca, Mg, Na, K and P in red amaranth was statistically insignificant among the treatments. On the contrary, the effect of foliar application of chitosan at different doses disclosed a statistically significant difference in S, Zn and Fe contents of red amaranth. The highest amounts of chlorophyll-a, carotenoids, total ash, S, and Fe in red amaranth were obtained from treatment T5. Finally, the study results concluded that foliar application of chitosan at 300 mg L-1 has a significant positive effect on the growth, yield, pigments, S, and Fe contents of red amaranth.