We developed a digital microfluidics platform for preparation of poly(lactic-co-glycolic) acid (PLGA) Nanoparticles (NPs). Droplets of PLGA in dimethylformamide were merged with droplets of deionized water by electrical actuation on a digital microfluidics device to form PLGA nanoparticles through nanoprecipitation. The platform we developed is automated and allows for preparation of polymeric NPs with small size and high uniformity. Using our platform, we were able to prepare monodisperse PLGA NPs as small as 115 nm with a polydispersity index (PDI) of 0.14 which can be challenging with conventional preparation techniques on the macroscale. Size of the prepared NPs can be tuned through proper choice of the volume ratio between the two merged droplets which controls the induced internal convection flow after merging. Concentration of PLGA in the dimethylformamide droplet also had an effect on the size and polydispersity of the formed nanoparticles. We believe our results prove the potential use of digital microfluidics for testing combinatorial synthesis of different polymeric NPs for various applications. This approach allows robust and automated screening of NP preparations using only few microliters of the reagents used, thus conserving precious and costly NP components and loaded therapeutic agents.