Abstract: Background and Objective: Mango malformation causes about 37% annually losses of mango all over the world. This study investigated the effect of nano-chitosan on vegetative growth, fruit set, yield, fruit quality and resistance of malformation of two different mango cultivars in sensitivity to malformation; Ewais (sensitive) and Zebda (resistant). Materials and Methods: This investigation carried out during the two consecutive seasons 2015/16 on mango trees (Mangifera indica L.) cvs. Zebda and Ewais, grown in a private orchard at Wadi El-Muluk, Sharkia governorate, Egypt to evaluate the effect of foliar nano-chitosan at 15 February before flowering on vegetative growth, fruit set, yield and fruit quality as well as resistance of malformation. A complete block design (two seasons combined) had used. Two way ANOVA used to compare the samples of different coating treatments. Results: Ewais cv. displayed the highest of their tested attributes in most cases as well as fruits number/tree and fruits yield/tree compared with Zebda cv. On the contrary, the content of carotene in leaves and fruit characteristics, as well as resistance to malformation percentage Zebda cv. was highly significant compared with Ewais cv. The obtained results, foliar nano-chitosan treatments increased fruits yield as number of fruit or weight/tree and decreased malformation percentage as well as improving studied attributes especially nano-chitosan 5 mL L–1 treatment. Conclusion: It is concluded that by using the nano-chitosan as a foliar spray on mango trees with concentration of 5 mL L–1 to improve the vegetative growth and fruit quality. Physical and chemical properties increase yield of the trees and showed more resistance of malformation.