Europium-ion and gadolinium-ion codoped Y3Al5O12 phosphors were synthesized via a reverse microemulsion process. The emission intensity and quantum yield of Y3Al5O12: Eu3+ depend on the codoping concentration of gadolinium ions. The significant enhancement in the luminance and quantum yield via codoping of Gd3+ ions imply efficient energy transfer from Gd3+ ions to Eu3+ activators. The microemulsion-derived Y3Al5O12: Eu3+, Gd3+ phosphors with small particle sizes and enhanced luminescence efficiency are demonstrated to hold application potential for flat panel displays.