Conversion has been of major interest to psychology and sociology. In contemporary psychology of religion and spirituality, it is viewed as a particular case of spiritual transformation. Down through the centuries, theology has seen conversion as the fruit of collaboration between human endeavor and God’s grace. This dimension of conversion has not been the subject of psychological research. Nonetheless, the scientific findings regarding conversion may help us better understand human nature’s interaction with Divine grace. This paper will present the history of conversion and selected theories and conceptualizations of conversion originating in human sciences which can be helpful in understanding human experiences around religious conversion.