Cerium-doped Y3Al5O12 (YAG):Ce3+ nanophosphor particles were synthesized using flame spray pyrolysis (FSP) from urea-added nitrate liquid precursor with different molar ratios of yttrium to aluminum. The effect of urea and Y:Al molar ratio in the liquid precursor on the crystallinity and luminescence properties of YAG:Ce3+ nanophosphors was studied. The cubic YAG structure was obtained after heat-treatment of as-prepared particles. The addition of urea leads to a higher flame temperature and helps in the formation of crystalline phase during FSP. A higher molar concentration of Al in the liquid precursor helped in better incorporation of the dopant atom in the lattice and also promoted the formation of YAG phase. Well-dispersed spherical particles with an estimated size of 50 nm were obtained by the process. The YAG:Ce3+ nanophosphors synthesized using urea and excess aluminum in liquid precursor showed better crystallinity and higher luminescence intensity.