The transition towards more sustainable business practices requires the changing of products, services, processes, policies and resources of organizations. Acknowledging the role projects play in these changes, the concept of sustainability should be integrated in the way projects are selected, prioritized, performed, managed, governed and evaluated. This requires the integration of sustainability in the organizational strategy, project portfolio management and project management. However, studies on sustainability in business describes the application of the concepts of sustainability mostly on the above-mentioned level in isolation, with little or no attention to the linkages between the strategy, portfolio and project levels. A conceptual framework is presented indicating the interlinking practices of integrating sustainability into the organizational strategy, project portfolio management and project management. From this framework, empirical studies can be developed, and guidance is provided for organizations that aim to improve this integration and thereby embedding the deeper implementation of sustainability into their policies and practices.