We are currently experiencing a revolution in the world of social impact with the rise of social enterprises that are blurring the line between not-for-profit and for-profit ventures. The Social Enterprise Alliance defines a social enterprise as an organization that “advances its social mission through entrepreneurial, earned income strategies.” Social enterprises can be both for-profit firms with a social mission and not-for-profit organizations that take a business approach to achieving their social mission (Social Enterprise Alliance 2005). Social entrepreneurship has been gaining significant momentum in the USA and Europe and is spreading to other parts of the world as well. Social entrepreneurs are working across a number of sectors, including international public health. For managers of nongovern­mental organizations (NGOs) and community-based organizations (CBOs) in developing countries, it is important to examine this new trend and determine whether there are elements of this new model that are appropriate for them. Increasingly we are seeing that many NGOs and CBOs working in the public health field are focusing on improving sustainability within a changing funding environment. In this chapter, I examine the reasons behind this new focus on sustainability, provide a definition of sustainability, offer suggestions for planning for sustainability, and identify how social enterprise strategies can assist NGOs and CBOs to build a financially viable organization.