Plant research is of great interest due to its unique health-promoting properties resulting from the use of herbs and the wide availability of compounds with potential medical significance. Many natural compounds with therapeutic activity have been identified and are still being intensively studied. Some of these substances have already been evaluated and clinically approved as anticancer agents. This chapter presents the latest information on natural compounds of plant origin and their potential use in photodynamic therapy (PDT). This approach, referred to as “green” photodynamic therapy, is based on the use of photosensitizers of plant origin or from other natural sources and excitation light in the visible range. PDT is a minimally invasive treatment method characterized by high precision. In recent years it has gained recognition as an innovative approach to cancer therapy, but it is also used in fields such as dermatology, ophthalmology, and the treatment of microbial infections. The procedure involves administering a photosensitizer (PS), which accumulates in cancer cells or tumor vessels, and then exposing them to light of the appropriate wavelength, which initiates the formation of reactive oxygen species (ROS). A key element of this therapy is the selection of the right PS, which determines the effectiveness of the treatment. Although many compounds have been discovered that perform this function, the search for new, more effective photosensitizers is ongoing. Compounds of natural origin play an important role here, as numerous photoactive substances present in plants and fungi show efficacy comparable to their synthetic counterparts. Thanks to the increasing number of identifications of natural products with photoactive properties, many new compounds can be expected to be discovered to serve as PS.