How do Small and Medium-sized Enterprises (SMEs) lack of resources engage in Corporate Social Responsibility (CSR)? Previous research pointed out that social capital can be applied to study how SMEs facilitate CSR. However, the existing literature has not yet further discussed how each dimension of social capital dynamically interacts with CSR. According to social capital theory, this paper conducts case studies on four Taiwan-based SMEs, including the O’right International Corporation. Our important findings are as follows. Firstly, to form cognitive social capital, founder’s belief, commitment, and values play a key role in driving SME’s engagement in CSR. Secondly, to effectively use relational social capital, SMEs tend to engage in environment-related CSR practices, such as lowering environmental pollution, and economy-related CSR practices, such as product and service improvement through cooperation with internal and external stakeholders. Thirdly, to establish internal and external structural social capital, SMEs are inclined to systematically and integratively engage in CSR. Lastly, the aforementioned three kinds of social capital will positively and dynamically impact on CSR, which in turn facilitates sustainable social capital forming a positive loop that benefits SMEs in building differentiable competitive advantage.