Organic non-linear optical Benzimidazolium salicylate (BISA) single crystals have been harvested from methanol solution by slow evaporation method. The grown crystals belong to the monoclinic crystal system with space group P21/c. Good crystalline nature of grown BISA crystal was confirmed by PXRD. The FTIR spectrum analysis affirms the presence of functional groups in BISA crystal. From the UV‒Vis-Absorption spectrum, the lower cut-off wavelength (356 nm) and its energy band gap and linear refractive index were calculated. Luminescence spectrum was recorded to explore the emission peak at 426 nm. The mechanical strength of BISA crystal was determined by Vickers microhardness tester and mechanical parameters like Elastic stiffness constant (C11), Knoop hardness (Hk), Fracture toughness (Kc), and Brittleness index (Bi) were calculated for the first time. Dielectric properties of grown crystals were systematically investigated for different temperatures. Further, electronic polarizability (α) were calculated using Penn analysis and Clausius‒Mossotti equation. Z‒scan measurement was taken to explore the third-order NLO properties of BISA crystal and calculated values was found to be β (3.856×10‒5 cm/W), n2 (1.7882×10‒9 cm2/W), and χ(3) (6.3088×10‒7 esu). For the first attempt, the BISA crystals were tested against five human pathogenic bacterial, i.e. Bacillus cereus, Staphylococcus aureus, Shigella flexneri, Vibrio cholerae, and Klebsiella pneumoniae. Existing results established that Benzimidazolium salicylate crystals might find useful applications in nonlinear optics and antimicrobial field. © 2020 Precarpathian National University. All rights reserved.