This study aimed to evaluate the occurrence patterns and role of volunteering in Brazilian protected areas in facing the scenarios of reduced public funds for conservation. Thus, we analyzed volunteer work documents in 210 Brazilian conservation units and carried out a meta-analysis on the proposed objectives, activities offered, the prerequisites for participation and the provisions offered to volunteers. Parks have the highest demand for volunteers (i.e. the type of protected area where volunteers are needed the most to perform volunteer work), as well as for the objectives, activities and prerequisites. Volunteering is motivated by objectives associated with providing practical experience, but in activities associated with public use, visitation and infrastructure. The desired profile is associated with adults with advanced education who have experience in the environmental sciences, and there is no incentive for participation by local resident. The provisions offered to volunteers are mainly related to work execution itself, such as accommodation, food and transportation, despite the relatively low supply of training courses and personal protective equipment. We argue that volunteer actions are being encouraged to meet both the need for professionals and the reduced public funds allocated to conservation. In this sense, this incentive has motivated volunteer precariousness, since the ideal volunteer activity motives are distorted, as well as the services rendered. Knowledge of this process is important to assist in planning public policies and initiatives for conservation, as well as in models for restructuring voluntary action that can achieve both the objectives of volunteer action (i.e. inclusion of the surrounding community and society in the conservation), as well as to contribute to advances in the ecology and in the effectiveness of natural area conservation.