The effects of direct contact with nature on pro-environmental attitudes, values and knowledge were assessed by taking college students on field trips at Parque Estadual Turístico do Alto Ribeira (PETAR), and applying a system of directed activities developed throughout 16 years. The changes in knowledge, values and attitudes were evaluated in these students (experimental groups) and other students who were not exposed to the field trips (control groups) through questionnaires which were applied before (pre-tests) and after the trip (post-tests). Meaningful differences were verified between the control and the experimental groups, as well as discrepancies between the pre- and post-tests applied to the experimental groups - a clear indication that the direct contact with nature affected the positioning of the students towards environmental matters. These outcomes reinforce the idea of the importance of contact with nature as a way of implementing pro-environmental behaviors.