National parks and other protected areas continue to grapple with the complexities of dual management mandates. Since the establishment of national parks one of the driving motivators in many parts of the world has been that these places provide opportunities for recreational activity and enjoyment by people. However, they are the major mechanism globally for the conservation of biodiversity and many parks have been established primarily for this purpose. Yet even within these areas tourism remains one of the activities permitted by management agencies. National parks have also traditionally received little funding to support conservation efforts and park budgets continue to decline. Consequently, for many nations tourism provides the foundations for their parks continued existence. National parks and tourism are therefore closely linked. The dependence on tourism and requirement for parks to become increasingly self sufficient is now a dominant feature in many countries, but what are the potential threats and opportunities associated with such land use in parks? I first review some of the principal threats to national parks arising from tourism (e.g. visitor use, infrastructure), and then place these in the context of potential benefits to parks. I present recent data on the importance of tourism revenue to parks and show how species conservation benefits from tourism to protected areas. I also explore other mechanisms that can deliver benefits and what strategies agencies are adopting to deal with these challenges globally.