The development of sulfur-containing pharmaceutical compounds is important in the advancement of medicinal chemistry. Photosensitizers (PS) that acquire new properties upon incorporation of sulfur-containing groups or individual sulfur atoms into their structure are not neglected, either. In this work, a synthesis of sulfur-containing derivatives of natural chlorophyllausing Lawesson’s reagent was optimized. Thiocarbonyl chlorins were shown to have a significant bathochromic shift in the absorption and fluorescence bands. The feasibility of functionalizing the thiocarbonyl group at the macrocycle periphery by formation of a Pt(II) metal complex in the chemotherapeutic agent cisplatin was shown. The chemical stability of the resulting conjugate in aqueous solution was studied, and it was found to possess a high cytotoxic activity against sarcoma S37 tumor cells that results from the combined photodynamic and chemotherapeutic effect on these cells.