Glycine phosphite (GPt) single crystal was doped with complexing agent allylthiourea, rare-earth, and metal ions (cesium and iron). The dopant concentrations were varied between 1 and 3 mol%. Influence of the dopants on the structural perfection was studied using the X-ray diffraction method. Effects of the dopants on the phase transition temperature were examined using the impedance analytical method. The optical properties of the as-grown crystals were studied using a UV spectrophotometer. The surface morphology and the presenting defects were also studied by the chemical etching method and the obtained results have been presented.