Cassia fistula L. and Duranta repens L. are medicinal plants which are widely used in treating a variety of diseases, including malaria. The purpose of this study is to synthesize chitosan nanoparticles of Cassia fistula L. leaves and Duranta repens L. fruit methanol extract as antimalarial drug and to determine the in vitro IC50 values. Plant chlorophyll and tannin contents of both extracts were eliminated, because they do not have antiplasmodium activity (IC50>100 mg/ml). Synthesis formula A, B, and P falls within the criteria of nanoparticles with particles size range of 80-475 nm. The formula with poloxamer 188 produced better particles sizes and uniformity than the formula with oleic acid. IC50 of BCP and BDP formulas are, respectively, 0.004 and 0.08 mg/ml, which indicates the potential as antiplasmodium drugs.