A novel second generation benzyl ester dendrimer silicon phthalocyanine (D-SiPc) was synthesized and encapsulated into amphiphilic block copolymers to form polymeric nanoparticles (D-SiPc@m). The cellular uptake and subcellular localization of D-SiPc@m in U251 glioma cells were studied by confocal laser scanning imaging. The cellular uptake of D-SiPc@m into U251 glioma cells reached the peak after being treatment for 6 h, and D-SiPc@m was localized into both mitochondria and lysosomes. The photodynamic efficacy of D-SiPc@m against U251 glioma cells was evaluated. D-SiPc@m exhibited high photo-cytotoxicity toward U251 glioma cells under laser irradiation. This polymeric nanoparticle could be a promising candidate for therapy of glioma.