In this paper, the feasibility to make molded glass–ceramics transparent in the second and third atmospheric window has been investigated. The thermodynamical and viscosity properties of the base glass have been measured confirming the possibility of generating crystals during molding at different temperatures. 71Ga nuclear magnetic resonance confirms that gallium plays the role of nucleating agent of gallium in this glass. Examination of X-rays diffraction patterns and optical properties indicates that the generation of nanocrystals of GeGa4Se8 allows the glass–ceramics to keep a wide transparency in the infrared range from 2 to 15 μm. The crystallization of large GeSe2 crystals of at higher temperature induces scattering and a reduced transparency window. The mechanical and structural properties of the as-prepared glass ceramics show an increase of toughness from 0.188 to 0.387 MPa m1/2 and elastic modulus from 22.7 to 26.55 GPa while the number and size of crystals increase. As a result, the preparation of molded IR glass–ceramics with high resistance to thermal and mechanical shocks has been clearly demonstrated.