Cinnamaldehyde (CIN), a well‐known botanical active compound but with low aqueous solubility and susceptible to degradation by oxidation reactions, was entrapped in monodispersed nanoparticles (NPs) that were assembled from chitosan (CS) and tripolyphosphate (TPP). Scanning electron microscopy/atomic force microscopy images declared the uniformed spherical shape of NPs with a size range of 60–80 nm, respectively. The ζ‐potential of the particles were observed to be positive (4.01 to 10.40 mV). Based on FT‐IR spectroscopy results, the electrostatic interactions between the active agent and CS/TPP were regarded as a motive for the formation of CIN‐encapsulated NPs. Thermal stability of the particles entrapping CIN compared with the pure CIN was verified by thermogravimetric analysis. The entrapment efficiency of CIN in polymeric nanoassemblies ranged from 7.47 to 27.42%. The ABTS radical scavenging evaluation certified the potency of this nanosystem in maintaining the antioxidant capacity of CIN. Practical applications Cinnamaldehyde (CIN) is a natural product that have antimicrobial/antioxidant activities. But due to its extremely low water solubility and sensitivity to external factors (such as temperature, light, and oxygen), its practical use in the food industry is restricted. This research aims at incorporating CIN into chitosan/tripolyphosphate nanoparticles synthesized by ionotropic gelation method for improved thermal stability as well as retaining the antioxidant activity and achieving its application in nutraceutical and functional food industries.