Herein, a promising infrared nonlinear optical (IR NLO) material, Li2ZnGeS4, was successfully synthesized in the typical quaternary diamond-like semiconductor (DLS) system. This material exhibits excellent performances including a wide band gap (3.49 eV), a high laser-damage threshold (LDT, 8 × benchmark AgGaS2), and a good NLO effect (0.7 × AgGaS2) with phase-matching behavior. Furthermore, based on first principles calculations, the theoretical results are in agreement with the experimental results. [ABSTRACT FROM AUTHOR]