Folkloric preparations of valerian roots have been used as sedatives/anxiolytics and sleep inducers since ancient times. Our country harbors thousands of plant species, which lack scientific information although many of them are used in folk medicine. We have studied hydroalcoholic extracts of an Argentine valerian (underground parts): Valeriana carnosa Sm. from Patagonia Argentina, known as Ñancolahuen in Mapuzungum language. We have already shown that they presented ligands for the benzodiazepine binding site of the GABAA receptor, increased the sleeping time induced by sodium thiopental and showed anxiolytic-like activities in mice. We evaluated in vitro the capacity of V. carnosa extracts to inhibit human and mice MAO-A. As it showed inhibitory capacity over these enzymes (IC50 (95%CI): 285.8 (212.6 to 384.2) μg/mL ethylic extract over hMAO-A; 1 mg/mL, 80% inhibition over MAO-A of mice´s brain homogenate), possible antidepressant effects were evaluated. Mice treated with V. Carnosa extract under acute (100 mg/kg, one i.p., injection) and chronic treatments (100 mg/kg/day, in drinking water, for 28 days) were evaluated in the tail suspension and locomotor activity tests. While the acute administration revealed no significant effect on mice, chronic treatment showed a significant antidepressant-like behaviour. Furthermore, locomotor activity of mice was not affected. V. carnosa could become a novel CNS herbal product for the treatment of depression and related disorders.