The infrared (IR) transmitting nanocrystallized chalcogenide glass only containing α-CdGa2S4 IR nonlinear optical crystallites, which were confirmed by x-ray diffraction and Raman scattering measurements, was fabricated through the controllable nucleation and crystallization of the glass with the composition 82GeS2∙18CdGa2S4 at a temperature of 325 °C far below the glass transition temperature (Tg:415 °C) for a long duration. A clear second harmonic generation (green light, 532 nm) could be observed in the transparent 82GeS2∙18CdGa2S4 nanocrystallized chalcogenide glass, demonstrating the IR frequency-doubling function of the prepared nanocrystallized composite material.