This research delves into the sustainability of nonprofit organizations in Canada. For the approximately 161,000 nonprofit organizations in Canada, the dominant organizational model is a stand alone agency that competes with others in the nonprofit, public and private sectors for the resources--monetary, human, intellectual--that it needs to operate. Working within a legal framework that goes back over 400 years, the nonprofit sector is at a juncture that will either see transformational change into more sustainable forms or widespread organizational failure. There are many challenges to sustainability in the nonprofit sector. Over half of the countrys nonprofit organizations report problems planning for the future and recruiting governance leadership to boards of directors. Just under half have problems obtaining funding. Not being able to attract skilled labor into nonprofit organizations stands as an additional challenge.Using a grounded theory approach, the study involved a series of focused interviews with senior administrators representing a diverse range of nonprofit organizations. Findings were conceptualized and coded. Seven theoretical categories were developed around the core category of boundary spanning and included: risk, learning organization, sustainability, credibility, relationships, organizational uniqueness and ethics. Links were made to existing theory including: social movement theory, political opportunity theory, social identity theory, self-categorization theory, common-in group identity model, and the between group helping model. These domains of theory share a concern with how an actor in the form of an individual or an organization, forms its identity and how that actor then interacts with others.The thesis finds that boundary spanning has the potential of being a fundamental process to ensure sustainability. Boundary spanning refers to the collection of processes and behaviours that allow for exchange cross the boundary of a nonprofit organization. To capture the intentionality of boundary spanning activities towards transformational change, the concept of metamobilization actors , is introduced. Combined with the commitment to the creation of ethical action in community by employees, metamobilization actors could provide Canadas nonprofit sector with new ways of addressing questions of long-term sustainability.