This paper discusses the role and function of the dai in the perspective of da'wah psychology. Da'wah is the duty of every Muslim. As preachers of course we want to be successful in achieving the task of da'wah. One form of success in da'wah is a change in a person's mental attitude. Da'wah psychology guides da'wah activities, so the purpose of da'wah psychology in the role and function of da'wah is to provide views about the possibility of changing the psychological behavior or mental attitude of the target of da'wah in accordance with the pattern of life desired by religious teachings. The role and function of the dai as a da'wah interpreter is one of the factors in da'wah activities which occupies a very important position in the success or failure of da'wah activities. Dai professionals who specialize in the field of da'wah, should have a good personality to support the success of da'wah, both spiritual and physical. The results to be obtained with the knowledge of this paper, it is hoped that we can carry out the task of da'wah with a psychological approach so that it is well understood the role and function of a dai as a preacher and the condition of the object of da'wah as mad'ū.