Voluntary blood donation remains insufficient in Bangladesh despite generally favorable attitudes among university students, raising questions about how Islamic teachings shape donation practices. This study examined how Islamic ethical frameworks, religious misconceptions, peer influence, and institutional mediation affect blood donation among Muslim students at the University of Dhaka. An explanatory sequential mixed-methods design combined a structured online survey of 50 Muslim students with semi-structured interviews involving five students, two imams, and the director of the Badhan Transfusion Centre. Quantitative data were summarized descriptively, while qualitative accounts were used to explain patterns concerning religious approval, motivation, Ramadan fasting, cross-faith donation, and institutional support. The findings show that participants generally regarded blood donation as consistent with Islamic teachings and associated it with sadaqah, preservation of life, and communal responsibility. Religious duty emerged as a major motivation, and most participants expressed inclusive humanitarian attitudes toward recipients from other religious communities. However, favorable religious approval did not always translate into regular donation. Uncertainty about donating during Ramadan, fear of violating religious obligations, informal peer messages, and uneven access to authoritative guidance created hesitation among some participants. The findings suggest that religion functions less as a direct behavioral determinant than as a moral resource whose effects depend on perceived permissibility, social norms, self-efficacy, and institutional opportunities. The study concludes that faith-sensitive education, credible guidance from religious and medical authorities, peer modeling, and recurring university-based donation programs can help convert Islamic ethical approval into sustained voluntary blood donation.