<p>The exocarp of kiwifruit is generally thin, making it highly susceptible to mechanical damage and pathogen infection during production, which significantly impacts fruit quality and postharvest storage. In this study, <i>Actinidia chinensis</i> cultivars ‘Jinfeng’, ‘Hort16A’, ‘Donghong’, and ‘Hongyang’ were used to determine the effects of foliar spraying 1-naphthaleneacetic acid (NAA) on exocarp thickness, peel structure, subcutaneous tissue cell layers, fruit quality, exocarp cell wall polysaccharide content, and related enzyme activities, aiming to explore technical measures to improve the thinness of <i>A. chinensis</i> exocarp. The results showed that 25&#xa0;mg·L⁻¹ NAA treatment significantly increased the exocarp thickness of ‘Jinfeng’ in the middle and late stages of fruit development, as well as the exocarp thickness of ‘Hort16A’ and ‘Donghong’ in the late stage of fruit development. NAA treatment induced a significant increase in subcutaneous tissue cell layers during early fruit development in ‘Jinfeng’, whereas no significant differences were observed in the other three cultivars. Additionally, NAA treatment significantly increased the single fruit weight of ‘Jinfeng’, ‘Hort16A’, and ‘Hongyang’, as well as the peel strength of ‘Jinfeng’ and ‘Hort16A’, but significantly decreased the soluble solids content in all four cultivars. Exogenous NAA treatment significantly increased the content of cellulose, hemicellulose, total pectin, and lignin, along with the activities of peroxidase and phenylalanine ammonia-lyase in the exocarp of most cultivars during the late fruit development stage, while also decreasing the activities of pectinase, cellulase, and polyphenol oxidase. These results provide a theoretical foundation for using NAA treatment to enhance exocarp thickness and improve fruit quality in <i>A. chinensis</i>.</p>