The aim of this work is to present results of both experimental and theoretical studies of 2–thioxo–3–N, (4–methylphenyl) thiazolidine–4–one. In this paper, we present the chemical synthesis of 2–thioxo–3–N, (4–methylphenyl) thiazolidine 4–one followed by spectroscopy study. The applying of ¹H and ¹³C nuclear magnetic resonance (NMR), ultraviolet–visible (UV–vis) spectroscopy, performed its structural characterization. UV–vis measurements showed absorption between 250 and 350 nm. The optical gap energy is calculated using the Tauc method, which comes out to be around 3.91 eV. Density functional theory (DFT) computations were adopted for the geometry optimization of this compound and to evaluate their static polarizability (the mean polarizability $⟨\alpha ⟩$ and the polarizability anisotropy $\mathrm{\Delta }\alpha$) and static first hyperpolarizability (the electric field–induced second harmonic generation (EFISHG) ${\text{β}}_{//}$ and the hyper–Rayleigh scattering (HRS) ${\text{β}}_{\text{HRS}}$) using several functionals. These static electrical properties are studied in detail. An inverse relation between the first hyperpolarizability and the HOMO–LUMO gap has been obtained for the 2–thioxo–3–N, (4–methylphenyl) thiazolidine–4–one. Based on these results, we can conclude that the synthesized molecule is considered as a good candidate for optoelectronic device applications.