A novel way is introduced to control polymerization routes and morphology of final polymer microspheres during the Pickering polymerization. Cetyltrimethylammonium bromide (CTAB)-modified silica and different initiators are used simultaneously to determine the initiation location, nucleation step, and morphology of final particles. As Pickering stabilizer, the CTAB-modified silica is characterized by dynamic light scattering. The size and distribution of the oil droplets stabilized by the silica nanoparticles is observed by optical microscopy. The resulted silica/polymer composite microspheres are characterized by scanning electron microscopy and transmission electron microscopy. The silica content is measured by thermogravimetric analysis. It is proven that both surface property of inorganic particles and type of initiators can greatly affect the polymerization routes and the morphology of the obtained polymer microspheres. Detailed formation mechanisms of several kinds of polymer particles are also proposed. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012