Background: Ayahuasca is a psychoactive ethnobotanical concoction that has been used for decades by indigenous groups of the Northwestern Amazon and by syncretic religious organizations for ritual and therapeutic purposes. In the last two decades, it is being used worldwide in evolving practices. Ayahuasca seem to therapeutic effects, but controlled studies are lacking. Moreover, its safety and toxicity are not completely understood. Objectives: To present an overview of the effects of ayahuasca based on the most recent human studies. Methods: Narrative review. Results: Ayahuasca administration in controlled settings appears to be safe from a subjective and physiological perspective, with few adverse reactions being reported. More frequent adverse reactions occur in non-controlled settings. Prolonged psychotic reactions are rare and seem to occur especially in susceptible individuals. Ayahuasca showed antidepressive, anxiolytic, and antiaddictive effects in animal models, observational studies, and in open-label and controlled studies. Discussion: Ayahuasca administration in controlled settings appear to be safe. Moreover, ayahuasca seem to have therapeutic effects for treatment-resistant psychiatric disorders that should be further investigated in randomized controlled clinical trials. However, medical complications and cases of prolonged psychotic reactions have been reported, and people with personal or family history of psychotic disorders should avoid ayahuasca intake.