There're many effects of mental illness both in establishment of marriage, during marriage and in dissolution of marriage. The existence of issues that need to be clarified in relation to these, the inaccuracy of some judicial decisions and the absence of a study that previously assessed the subject systematically encouraged the preparation of this work. In the study, the effects of mental illness on marriage had been assessed according to the stages of establishment, continuation and termination of marriage, by trying to clarify the problems and examining the judicial decisions that weren't appropriate. Mental illness may or mayn't remove mental competence in some cases and this quality of it had been considered in the present study.