In this chapter polymeric nanoparticle preparation methods are explained briefly. There are some commonly used methods for nanoparticle preparation such as the emulsion solvent diffusion method, salting out method, nanoprecipitation method, supercritical fluid method, and spray drying. The disadvantages of these methods in general are that they cannot yet be synthesized into nanoparticles with the desired biocompatibility, especially the emulsion solvent method we prefer in our laboratory. This method may be more advantageous if biopolymers are synthesized using organic solvents. As the purpose of this chapter, information about general methods for the preparation methodology of vaccine and drug active ingredients and nanoparticles to be used together with nanoparticles is presented. As a result, although there are many polymer synthesis methods and new methods continue to be developed, the most preferred methods are concluded in this chapter.