This paper aims to provide new insights into possible managerial choices and practices for successful implementation of social innovation, building on mechanisms identified in open innovation literature. While validity of openness in the management of innovations addressing social challenges have been proved in few works, effective modes for meeting social needs by leveraging on external sources of knowledge still need an in-depth investigation and empirical evidence. Aiming at a comprehensive understanding of how companies adopt open innovation practices for social aims and the context characteristics affecting related choices, the research design is qualitative and compares two case studies from for-profit and not-for-profit sectors. Results show that practices such as external networking and joint co-creation can be applied for different social challenges where engaging stakeholders (especially end users) and scout and transform opportunities for innovation. A for-profit company tends to use also dedicated practices such as specialised services from intermediaries for recognising opportunities, while companies from not-for-profit sector rely on internal sources and established collaborations. The analysis of practical modes for effective management of social innovation provides a valuable perspective for innovation managers and researchers focusing on managerial issues requiring openness to achieve systemic social change.