This chapter seeks to answer two interrelated questions: (1) If a religious experience is caused by a mental disorder, is it plausible to construe that experience as a genuine religious experience? (2) Does it make a difference to (1) if mental disorders are caused by brain dysfunctions? I will argue that the answer to both these questions should be a negative one. I will begin by defining my terms and then proceed to give an argument for a negative answer to (1). If a mental disorder is causing a religious experience, then that experience cannot function as a source of knowledge about religious realities. This is because many mental disorders involve epistemic dysfunctions that disqualify them as trustworthy sources of beliefs. In the following section, I will consider some objections to this argument. These objections mainly revolve around the concept of function. Finally, I will consider question (2), namely, whether the argument is stronger, if mental disorders involve brain dysfunction. Somewhat surprisingly, I will suggest a negative answer here as well. When we adopt a plausible notion of ‘brain disorder’, the potential existence of a brain disorder adds nothing to the epistemic evaluation of psychological mechanisms. The concluding section of the article draws some lessons for the neuroscientific study of religion and religious experience.