Many species of plants and mushrooms exist that, when consumed, can induce poisoning in individuals, causing a range of side effects. As the toxins do not always correspond to an antidote, it is important to have the ability to identify each harmful species to determine the appropriate treatment. This review gives an overview of some of the more prevalent toxic plants and mushrooms, detailing their principles of toxicity, recommendations for immediate stabilization, keys to proper diagnosis and definitive therapy, and patient disposition and outcomes. Figures show photographs of the various toxic plants and mushrooms featured. Tables show a list of toxic species for both plants and mushrooms, including their common names, the toxins contained within, their effects, and the corresponding antidote (if any). This review contains 16 highly rendered figures, 2 tables, and 44 references.