Jackfruit leaves extract (Artocarpus heterophyllus Lamk.) which contained flavonoid as an antioxidant was unstable and sensitive to environmental conditions. Preparation of nanoparticles loaded jackfruit leaf extract aimed to increase the antioxidant activity through optimal delivery system and maintain the stability of flavonoid from jackfruit leaf extract. Nanoparticle preparation used an ionic gelation method with chitosan, sodium alginate, and variation of calcium chloride. Characterization of nanoparticles were particle size, polydispersity index, efficiency of encapsulation, zeta potential, and XRD analysis. Based on the result, the highest percent of encapsulation efficiency in the nanoparticles with the amount of calcium chloride 40 µl was 90,76%. The characterization of nanoparticles, particle size was 244,2 nm, polydispersity index was 0,22, and zeta potential was +26,4 mV. The XRD pattern of nanoparticles loaded jackfruit leaf extract showed jackfruit leaf extract encapsulated into nanoparticles. Antioxidant activity of jackfruit leaf extract increased after encapsulation as indicated by the IC50 for nanoparticles of jackfruit leaf extract was 10,13µg/ml which indicates high antioxidant.