The paper presents the X-ray photoelectron spectra (XPS) of the valence band and core levels of the semiconductive Bi2S3 single crystal, which shows anomalies in various physical properties and weak phase transitions without change of symmetry. The XPS were measured with monochromatized Al Kα radiation in the energy range 0–1400 eV and the temperature range 160–460 K. The valence band is located 0.55–6.5 eV below the Fermi level and shows non-linear dependence on temperature. Experimental energies of the valence band and core levels are compared with the results of theoretical ab initio calculations of the molecular model of the Bi2S3 crystal. The chemical shifts in the Bi2S3 crystal for the Bi and S states are obtained. Results revealed the origin of a weak polarity of the crystals at room temperature, which results in anomalies in the physical properties, and shifts the Fermi level and all the electronic spectrum.