This study, which draws on extensive fieldwork and local sources, examines the supernatural beliefs (i.e. related to demonic and magical forces) among Chinese Muslims in the modern-day province of Qinghai, China. The core argument presented in this article is that the supernatural realm is a space where Muslims draw lines and form their perceptions of orthodox Islamic beliefs and practices, oftentimes in contrast to Muslims of other sects, as well as other religions and the Communist state itself. In addition, it is a space where these boundaries concerning orthodoxy and propriety are transgressed, usually out of some spiritual necessity or because of interactions with other diverse non-Muslim religious traditions. This dynamic of boundary-making and -breaking in relation to the supernatural showcases the porous character of religious beliefs and practices among Chinese Muslims in immensely diverse environments like Qinghai.