Microfluidics is a promising system for efficiently optimizing the experimental conditions for preparing nanomedicines, such as self-assembled nanoparticles. Poly(lactic- co -glycolic acid) (PLGA) nanoparticles are promising drug carriers allowing sustained drug release. Here, we encapsulated the model drug curcumin, which has many pharmacological activities, into PLGA nanoparticles and investigated the effects of experimental conditions on the resulting PLGA nanoparticles using a microfluidics system with a staggered herringbone structure that can stir solutions through chaotic advection. The total flow rate and flow rate ratio of the solutions in the microfluidics system affected the diameters, polydispersity index, and encapsulation efficiency of the resulting PLGA nanoparticles and produced small, homogenous PLGA nanoparticles. The incorporation of polyethylene glycol (PEG)–PLGA into the PLGA nanoparticles reduced the particle size and improved the encapsulation efficiency. Initial burst release from the PLGA nanoparticles was prevented by the incorporation of PEG2000–PLGA. Curcumin-loaded PEGylated PLGA nanoparticles showed cytotoxicity similar to that of other formulations. This microfluidics system allows high throughput and is scalable for the efficient preparation of PLGA nanoparticles and PEGylated PLGA nanoparticles. Our results will be useful for developing novel PLGA-based polymer nanoparticles by using the microfluidics.