Slow evaporation procedures were used to create high-quality organic crystals of guanidinium carbonate (GC). The crystal crystallises into a Tetragonal system with space group P41212. according to X-ray diffraction. The Fourier Transform Infrared Analysis verified the functional group present in the produced crystal. According to the optical analysis, the UV cutoff wavelength is around 239 nm. The developed crystal's optical band gap was discovered to be 5.34ev. The title compound's mechanical behaviour was examined using the Vicker microhardness tester. Nd:YAG laser measurements were made to determine the generated crystals' surface laser damage threshold. TGA/DTA analysis have been used to study thermal behaviour. By using the agar diffusion method, the antifungal activity was also targeted for examination against two well-known fungi, such as E. coli and Staphylococcus aureus.