Single crystals of pure oxalic acid and oxalic acid doped with tryptophan have been grown by slow evaporation method. These crystals are characterized by single crystal XRD, Powder XRD, FT-IR and UV-Visible spectral analyses. Effect of tryptophan as an impurity on the properties of oxalic acid has also been investigated. X-ray diffraction analysis indicates the crystal system as monoclinic. The functional groups have been identified using Fourier transform infrared spectral analysis. The UV-Vis spectral analysis shows that these crystals have wide transparency range in the entire visible region. The pure and doped crystals were analysed by the antimicrobial activity study against the gram positive and gram negative bacteria by disk diffusion method.