Don Quixote, the most outstanding novel of the Spanish literature, represents a documentary source widely used among those specialists who intend to deepen in the knowledge of the late Renaissance society. In this sense, Don Quixote has been also studied from a medical perspective, including a general therapeutical view (oils, ointments, balms, poultices, syrups and other pharmacy preparations). We have tackled Don Quixote from the phytotherapeutic and ethnopharmacological perspective, a barely explored field. In this work, we intend to study the medicinal plants used during the Cervantine time for the treatment de multiples diseases (sedatives like opium, laxatives and emetics like hellebore, tonics and irritants) and we analyze the specific herbal therapies (balms, purgatives and emetics, ointments and poultices), which Cervantes reveals to us in his novel. Among them, the rhubarb root (Rheum spp. or Rumex spp.) should be highlighted, as well as the seeds of gopher spurge (Euphorbia lathyris), chicory (Cichorium intybus) and rosemary (Rosmarinus officinalis), primary component of the famous Balsam of Fierabras. Also, we have examined the possible scientific influences, which might have inspired Cervantes in this field, mainly the work of Andrés Laguna (Dioscorides' Materia Medica).