Abstract: Single crystals are Bis Glycine Cobalt Sulfate (BGCS) recently investigated nonlinear optical materials were grown by slow evaporation techniques. Optical absorption of the crystals of BGCS has been measured at room temperature from which the optical band gap has been determined using the absorption spectrum as 5.90 eV. Vibrational modes of grown crystals were conformed by FTIR spectrum. The optical absorption spectrum shows that the UV cut-off wavelength for the grown crystal is at 240 nm. The optical constant (α, K, R) were also evaluated.