A detailed investigation of Valsartan`s light-induced degradation is reported. Based on UPLC-HRMS studies of stressed solutions several degradation pathways are proposed. Some of the proposed structures were obtained by forced degradation experiments. Examination of analytical data including crystal structures allowed for structural revision of one literature-known degradant. In addition, irradiation under aerobic conditions revealed further degradative pathways leading to two previously unknown decomposition products. Mechanistic considerations regarding their origin helped to identify structural weak points of Valsartan under the influence of light