Objectives:The purpose of this study was to investigate the effect of andrographolide-carboxymethyl chitosan nanoparticles formation on the physical characteristics, in vitro release profile and in vivo antimalarial activity of andrographolide.Materials and Methods:Nanoparticles were prepared by ionic gelation method-spray drying using CaCl₂ as the crosslinker with a composition of drug: polymer: CaCl₂=40: 250: 100. The obtained particles were evaluated for its size and morphology; physical state, drug content, in vitro drug release and in vivo antimalarial activity on Plasmodium berghei infected mice. Results:The results of DTA and XRD showed that nanoparticle systems had a lower melting point and lower crystallinity degree. The drug dissolved from the nanoparticles was increased up to 6.5 times and the in vivo antimalarial activity was 1.65 times higher compared to andrographolide.Conclusion:The formation andrographolide-carboxymethyl chitosan nanoparticles affected the physical characte-ristics of andrographolide. The decrease crystallinity of andrographolide resulted in a lower melting point of andrographolide. Such changes provided a positive impact to the drug dissolution and then its activity.