The striatum (St) integrates cognitive, motor and limbic functions and plays a critical role in the processing of emotions, motivation and rewards, and may undergo several morphophysiological changes in neuropsychiatric diseases. Depression, a complex psychiatric disorder, affects millions of people around the world and leads to an increased risk of suicide, decreased quality of life and functional impairment. Conventional treatments require prolonged use, leading to drug resistance, so new treatments and therapeutic strategies have been widely studied. Ayahuasca is a tea used in indigenous religious rituals, which has psychoactive properties. Its medicinal use in depression has shown promising results in preliminary studies. Our objective was to morphoquantitatively evaluate the effects of ayahuasca on St in an already validated model of juvenile depression induced in a non-human primate. Six marmosets were used, divided into groups of 2 animals. One group was kept in family life (GF) and two groups were socially isolated (GI). Social isolation was carried out for each animal, separating it from all others in the colony. One of the isolated groups received doses of ayahuasca tea (GT) 5 days before and three times during the isolation period, while the other groups received the same dose of saline as a placebo. After 120 days of experimentation, euthanasia and transcardiac perfusion were performed. The brains were sectioned and stained with thionin using the Nissl method. We carried out the St evaluation using stereological techniques to verify the total volume, neuronal volume density, estimate the total number of neurons and neuronal volume. For all measurements and estimates, equidistant sections of the caudate (Cd) and putamen (Pu) were analyzed, selected by systematic and uniform sampling. The GI and GT presented increased volumes when compared to the GF. The GI showed an increase in neuronal number compared to the GF. The treatment appears to have partially controlled this increase. Isolation increased neuronal distribution in St, and Ayahuasca reversed it. Our data show the decrease in volume of St neurons and the neuroregenerative/neuroprotective action of Ayahuasca in a model of juvenile depression in non-human primates subjected to social isolation, as evidenced by the partial restoration of normal neuronal volume and number.