Well-defined NaGd(MoO 4 ) 2 octahedral microcrystals have been synthesized via a simple hydrothermal route. The whole process was carried out under aqueous conditions without the use of any organic surfactant, solvent, or catalyst. During the synthesis process, the pH value of the initial solution plays a crucial role in determining the morphology and particle size of the final products. The as-obtained NaGd(MoO 4 ) 2 :Ln 3+ (Ln=Eu, Tb, Dy, and Sm) phosphors show intense red, green, yellow, and orange–red emissions under ultraviolet excitation, which can be confirmed by the CIE coordinates. The as-synthesized luminescent materials may find potential applications in fields of fluorescent lamps, light-emitting diodes (LEDs), and optoelectronic devices.