Contact with nature increases human health and well-being by stress reduction, positive-emotionelicitation, and attentional restoration. Despite the outstanding Brazilian biodiversity, we are unaware ofstudies linking nature experiences to welfare. Herein, we applied cognitive tasks and emotional self-reportsin 33 subjects, before and after a 30-minute walk in a nature trail at Parque Nacional de Brasília, and compared them with the same tests applied before and after a 30-minute walk in Brasilia´s downtown. We recorded improvements in emotional self-reports after nature experience, while the urban exposure caused decreases in self-reported happiness and increases in negative emotions. These results highlight the relevance of natural settings for cognitive and emotional well-being and the need for a better understanding of the relationships between nature and human health. The recognition that mental health is an ecosystem service can improve the arguments for nature conservation, and the quality of life and public health.