Abstract Organotins are popular among chemists due to their potential biological properties against bacteria, fungus, and cancer cell lines. In particular, organotins have been utilized in chemotherapeutic applications. Compared to cisplatin, organotins give more favorable toxicological profiles and better cytotoxicity and antiproliferative activities. However, organotins have limited biological applications due to their poor water solubility. In this study we synthesized a diphenyltin complex (Diphenyltin Dioxalate) that possesses partial ionic characteristics, by reacting a diprotic carboxylic acid, with triphenyltin chloride in the presence of di-isopropylamine. A tin-carbon cleavage reaction was observed, as IR/NMR spectroscopy and X-ray Crystallography studies showed that diphenyltin dioxalate was successfully obtained in the reaction. Post synthesis solubility tests were performed to examine diphenyltin dioxalate’s water-soluble nature, compared to its precursor triphenyltin. Diphenyltin dioxalate was then tested to examine its cytotoxicity and antitumor activity on human glioblastoma cell model (T98G) and a normal human oligodendrocyte cell model (MO3.13). Further studies with the complex will consist of synthetic mechanistic studies on the Sn-C cleavage. Citation Format: Jade Witter, Xuequing Song, Alexandra Taraboletti, William Li, Tajera Henry. Design and in vitro antitumor analysis of a novel diphenyltin complex (diphenyltin dioxalate) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4059.