Abstract Tiger nut (Cyperus esculentus L.) is an ideal raw material for oil extraction, but starch-rich tiger nut meal, a by-product of oil extraction, has not been fully utilized. For this, starch was isolated from tiger nut meal, and then starch nanoparticles were prepared by gelatinization, ultrasonication and nanoprecipitation under different conditions. The preparation parameters were optimized by measuring the particle size with dynamic light scattering, and the physicochemical properties of native starch and nano starch were evaluated. The results showed that, compared to native starch, starch nanoparticle (nano starch) has a higher amylose content (39.05%), solubility (56.13%), and swelling power (58.01%). Furthermore, native starch and nano starch were esterified with octenyl succinic anhydride (OSA), respectively, conferring amphiphilic properties. The effects of OSA modification on the resistant starch content, thermal properties, and microstructure of starches were characterized. The resistant starch content of tiger nut native starch increased by 10.81% after OSA modification, while the resistant starch content of OSA nano starch increased to 37.76%. Compared to native starch, the gelatinization temperature of OSA nano starch decreased by 2.7 °C and nano starch decreased by 5.68 °C. OSA modified nano starch showed a unique microstructure, such as a slender fiber structure and a regular oblate structure. The hydrophobic OSA groups aggregated to form hydrophobic cavities with a hydrophilic surface in the aqueous phase. The findings presented in this investigation provide a better understanding of the design and development of OSA nano starch and provide valuable guidance to further enhance the added value of tiger nuts and future applications in the food industry.