Single crystals of l-leucine l-leucinium picrate (LLLLP) were grown by the slow evaporation solution technique. The crystal system and lattice parameters were confirmed by single crystal XRD. The UV–vis transmission spectra were recorded for the grown crystal and relative second harmonic generation (SHG) efficiency was measured for the first time. The relative SHG efficiency of the material was found to be ∼1.5 times higher than that of KDP. The crystalline perfection of the grown crystal was assessed by high-resolution XRD. The functional groups present in the crystal were confirmed by FT-IR analysis. The thermal studies were carried out and show that the grown crystal is stable up to 195°C.