The certificate of incompatibility is a title that the legislator has established for the decisions of the family court in the matter of divorce. Since there is no such title in the traditional division of court opinions, therefore, it is important to examine its nature and determine its position among the judicial decisions of the family court. The present article has studied the certificate of incompatibility in Iran's legal system with a library method and in a descriptive-analytical way, including its background, nature, cases of issuance and implementation, and finally reached the conclusion that in explaining the nature of the certificate of incompatibility It is necessary to distinguish between consensual divorce and divorce at the request of the husband. In consensual divorce, the nature of this certificate is merely the reflection of the couple's lack of compromise and their agreement, in this case, the court does not make any judgment. However, in divorce at the request of the husband, if the man's absolute authority in the divorce is accepted, the family court proceedings will be limited to hearing his opinion, referring the couple to arbitration and determining the wife's financial rights. In this type of proceedings, Judge will have a passive role and as a result, the certificate of incompatibility cannot be considered as a "verdict". However, in case of acceptance of the adjustment of the husband's right to divorce, the type of proceedings of the family court, similar to the case of the wife's divorce case. In this case, the nature of the decision of the family court, which originates from an arbitration matter, is not a mere certificate, but has the characteristics of a judgment.