The research objectives are to study the implementation of Islamic Corporate Social Responsibility (i-CSR) values in BMT UGT Sidogiri, an Islamic microfinance institution in Indonesia based on Islamic boarding school or pesantren. This research employed a post-positivist paradigm. Data observation was performed by conducting an in-depth interview with several informants. The data analysis utilized an interactive model technique. The research results showed that i-CSR was successfully implemented in the Islamic microfinance institution based on Islamic boarding school due to the mutual passion (convergence) with conventional CSR typologies. The convergence is in two ways, firstly managerial behavior that focuses on protecting company stakeholders, second, creating sustainable corporate values through effective and efficient business activities. The orientation is the creation of a social role based on justice and sustainable development. The convergence is mainly in the dimensions of economic, legal, ethical and philanthropic responsibilities. The Islamic values have enriched the implementation of i-CSR as the form of practicing the teachings of Islam and evidence of human servitude to God so that the behaviors become worthy of worship. The implementation of i-CSR focused on the Islamic teachings. Compliance to Islamic jurisprudence and apply it in business activities became a divergent element of conventional CSR concept.