Despite the potential of CSR to drive relationship-building and improve the relationship performance, extant research to integrate corporate social responsibility (CSR) and relationship marketing has been scarce. This study investigates the relationship between CSR, as a relationship-building strategy in business to business (B2B), and relationship quality, which is the key variable mediating relationship performance in relationship marketing. Previous studies have only examined the relationship between CSR and individual variables that constitute relationship quality, and also the relationship among the factors of the relationship quality was not confirmed. Further, relationship marketing strategies suggested in the extant studies are insufficient to provide the implementation guidelines in practice. Specifically, in this study, the authors conceptualize CSR as a relationship-building strategy and examine how two CSR activities of business practice CSR and philanthropic CSR have an impact on the relationship quality, the inter-relationship among the factors of the relationship quality, and the relationship between the factors of the relationship quality and relationship performance. As a result of the empirical analysis with 208 B2B companies, it was found that the business practice CSR activities had a positive effect on relationship satisfaction, trust, and relationship commitment. Furthermore, the authors also confirmed that the philanthropic CSR activities in terms of the secondary stakeholders who have no direct interest, influences on the relationship satisfaction and relationship commitment. The relationship between the quality factors of relationship quality were analyzed to suggest the causal relationship as “relationship satisfaction → trust → relationship commitment”. Finally, in the relationship between relationship quality and relationship performance, the influence of relationship satisfaction on relationship performance was not statistically significant whereas trust and relationship commitment was found to have a positive effect on relationship performance. This study not only highlights the proposition of integration of CSR research and relationship marketing domain in B2B transaction relationship, but also practically provides that CSR can be used as a crucial relationship marketing strategy.