The agricultural industry worldwide is facing several challenges including environmental pollution problems (soils and water) caused by the unsuitable control on the use of agrochemicals. Recently, nanotechnology has become an option to improve the existing crop management techniques. Polymer nanoparticles can be used for storage and controlledrelease of agrochemicals, such as pesticides and fertilizers. In this regard, chitosan nanoparticles have been considered for agricultural applications due to the capability of size control at the nanoscale and porosity control capability, in addition to biodegradable and biocompatible characteristics. On this basis, this work focuses on the development of a sizecontrolled synthesis method for chitosan nanoparticles for further use as a platform for the controlled-release system of agrochemicals. The chitosan nanoparticles were synthesized by polymerization using methacrylic acid in water. Several chitosan precursor concentrations (0.2- 0.8 wt.%) were evaluated in order to manipulate the size of produced nanoparticles. The hydrodynamic diameter of those nanoparticles was determined by using a Malvern Zetasizer and the suspension stability trough zeta potential measurements. The morphology and geometrical size were investigated by Transmission Electron Microscopy (TEM). Chitosan nanoparticles size was around 17 nm when a precursor 0.2 wt.% chitosan solution was used. X-ray diffraction and Fourier Transform Infrared Spectroscopy techniques confirmed the chitosan nanoparticles formation and its interaction with functional groups of methacrylic acid.