o-Phenylenediaminium bis-hydrogen phosphonate (P2HP) was synthesized and single crystals were grown by slow evaporation method. The crystal structure, crystalline perfection and morphology of P2HP were studied and interpreted from XRD studies and WinXMorph program respectively. UV–Visible transmittance was performed to estimate the transmittance and bandgap energy. Laser induced damage threshold study was performed for the grown crystal. Third order nonlinear optical parameters of P2HP crystal was estimated by Z-scan test.