Various researchers have demonstrated the importance of having suitable partners for effective CSR implementation, making the selection of appropriate CSR partners an increasingly important issue for companies’ CSR development. However, most of the existing research on CSR partnerships tends to focus on the collaboration between corporations and non-profit organizations, with less attention paid to the diverse partnerships between different types of organizations. This research explores how companies choose their partners and methods of collaboration under different CSR partnerships with in-depth case studies of three leading companies in Taiwan that have been actively engaged in CSR. The findings of this research led to the proposal of a CSR Partner Selection model, which reveals the dynamic processes and specific criteria of screening and selecting suitable partner(s) for companies’ CSR projects. This research contributes to the existing literature by expanding our knowledge regarding cross-organization CSR partnerships, and also provides important implications for organizations seeking CSR partnerships in practice.