In this study, novel Li2ZnSnS4 (LZSS4) thin films have been manufactured using the inexpensive spray pyrolysis system. The study of the X-ray diffraction (XRD) of the LZSS4 films demonstrated that these LZSS4 samples have crystalline structures with monoclinic phases. The elemental analysis of the LZSS4 samples refers to the presence of Li, Zn, Sn, and S in the LZSS4 samples. Their ratio is near 2:1:1:4. Meanwhile, the linear optical study of the LZSS4 samples indicates that the LZSS4 samples have a direct energy gap (Eg), and the growth of thickness led to a decrease in the Eg values from 1.73 eV to 1.48 eV. Conversely, the refractive index of the LZSS4 samples increases from 2.56 to 4.18 by raising the thickness of the investigated samples. Moreover, the Wemple-Didomenico single oscillator model was applied to compute the dispersion parameters of the LZSS4 samples. It was found that the dispersion energy, Ed, improved from 15.87 to 17.26 eV, and the oscillator energy, Eo, dropped from 6.44 to 4.91 eV by raising the thickness from 261 to 486 nm. Also, the study of the optoelectrical and nonlinear optical parameters refers to enhancing the non-linear refractive index (n2), optical resistivity (), optical carrier concentration (), relaxation time (τ), and optical mobility (). [ABSTRACT FROM AUTHOR]