The mystical causes of diseases related with the Igbo traditional belief system are briefly investigated in this research. The specific goals are to look at mystical/spiritual reasons and techniques of fighting diseases, as well as their benefits and drawbacks in terms of disease therapy. For data analysis, the study used a qualitative phenomenological research design and a descriptive approach. Personal interviews were the major source of data collecting, whereas library materials were the secondary source. According to the study, several mystical forces in Igbo cosmology, sorcerers, Ogbanje, curses arising from the violation of taboos and oaths are to be blamed for untimely deaths and sicknesses befalling people. As a result, even in the face of western Germ theory, the Igbo belief in mystical causes of disease has proven that Germ theory, as far as the Igbo traditional conception of disease causation is concerned, does not satisfy the Igbo belief in what causes diseases, as some diseases have defied western medication. The study proposes, among other things, that hospitals in Nigeria should take into account mystical agents as well as pathogenic agents in order to provide proper and adequate treatment for the people who believe in such traditional approached.