Social media have influenced millennials of "ulama" or Muslim scholars in "fatwa" production. They access and use online knowledge to make daily "fatwa" according to community requests. However, limited is known about how the millennial "ulama" acquire and use the knowledge. We carried out an interpretive case study using a theoretical lens from knowledge creation and use in an information technology context and Islamic sociology. Data were gathered through in-depth interviews involving 36 millennial "ulama" as informants. The interviews were used to understand the respondents' perspectives on knowledge acquisition and use in their daily "fatwa" making within a provincial level of Indonesia Ulama Council (MUI). The findings show that Indonesia's millennial "ulama" have intensively acquired and trusted online Islamic knowledge. Also, they construct and use knowledge from online social network interaction in daily "fatwa" making. This study has implications for the simplicity of Islamic knowledge acquisition and "fatwa" making. Online knowledge acquisition might have reduced the roles of traditional Islamic education institutions and "muftis." Therefore, further research should examine how new knowledge sources have caused this reduction.