Private sector bodies can be important owners and managers of conservation areas. However, little is known about the extent, scale and scope of private protected areas. Understanding and defining the characterizations of private protected areas are problematic, as private sector involvement in protected areas can involve an array of different tenure arrangements, management approaches and levels of control. This review examines the challenges of developing protected area categorization beyond the traditional state-led model. We review private protected areas in Kenya and Tanzania, exploring their tenure, the nature of the private sector organizations managing them, and the extent of control exercised within them. Drawing on this we develop a working typology with the aim to encourage further discourse amongst the conservation community on the emerging phenomenon of private protected areas.