Eu2+-doped CaMgSi2O6 phosphor was prepared by depositing mixed hydroxides of Ca, Mg, and Eu over spherical SiO2 particles (300 nm) pre-coated with polycations (polyethyleneimine), followed by calcination at 1200°C in a reducing atmosphere. The prepared phosphor showed intense blue emission, ascribable to the 4f7-4f65d transition of Eu2+. In contrast, the luminescence intensity of the phosphor was considerably decreased when prepared without polycations. It was suggested that negatively charged hydroxides are deposited on positively charged SiO2 surfaces pre-coated with polycations through electrostatic self-assembly interaction. On calcination, the hydroxide shells react with the SiO2 cores to produce Eu2+:CaMgSi2O6.