<p>This paper reports the study on the synthesis, characterization, linear and nonlinear optical (NLO) properties of the Schiff base N’,2-bis((E)-4-hydroxy-3-methoxybenzylidene)hydrazine-1-carbohydrazide (HPMC). The Schiff base was characterized by UV-Visible absorption, FT-IR, ¹H and ¹³C NMR, confocal Raman and Mass spectroscopy techniques. The chemical compounds of the Schiff base were identified by FT-IR and Raman Spectroscopy. The molecular weight of the compound was confirmed by Mass spectroscopy. The chemical shift with total number of protons and carbons of the Schiff base HPMC was calculated using ¹H and ¹³C NMR spectroscopy. Z-scan technique was used to measure the third-order NLO features of the sample, which revealed a significant third-order NLO susceptibility of 7.19 × 10^− 7 esu. The nonlinear refractive index and absorption coefficient of HPMC was ascribed to saturable absorption (SA) and self-defocusing. Furthermore, the experimental results were validated by theoretically using density functional theory (DFT) B3LYP functional with the 6-311G(d, p) basis set. The molecular polarizability, electrostatic potential, frontier molecular orbit of the Schiff base was validated theoretically. The experimental and theoretical results divulged that the Schiff base N’,2-bis((E)-4-hydroxybenzylidene)hydrazine-1-carbohydrazide was a potential NLO material for photonics and optoelectronics applications.</p>