A key strategy to reduce habitat loss and fragmentation involves the establishment of protected areas (PAs). Worldwide, c. 13% of land lies within PAs, but only 6% is subject to the more restrictive International Union for the Conservation of Nature (IUCN) categories I-IV. Private PAs may contribute to this figure, but require general guidance principles for their management. The Brazilian ‘Private Natural Heritage Reserves’ (RPPNs) constitute an example of good PA management, employing seven principles that should guide the creation of all private PAs. RPPNs have legal status and long-term security, allow only for indirect human uses, and provide a strategic conservation role in highly fragmented landscapes by improving connectivity. However, RPPNs are virtually absent from the World Database on Protected Areas, and given Brazil's continental size, and the considerable and increasing number of RPPNs in Brazil, this omission has the potential to skew accurate quantification of the area of land subject to strict protection. The RPPN model can make an important contribution to the discussion of the role of private PAs in conservation, especially in the tropics.