In Iran's legal system, "third party objection" means the objection of a person who was not a beneficiary in a lawsuit between two other people, but the judgment issued in that lawsuit harms his rights. A subordinate third party is someone whose interests are indirectly dependent on the outcome of the original lawsuit. In other words, the verdict issued in the main lawsuit indirectly damages his rights. The objection of the subordinate third party is raised when one of the following conditions exists: the judgment issued in the main lawsuit indirectly damages the financial or non-financial rights of the subordinate third party. The secondary third party was not present in the main lawsuit and did not have the opportunity to defend his rights. The verdict issued in the main lawsuit is against the law or Shariah standards. The dependent third party must submit the third party's objection petition to the court that issued the decision within 20 days from the date of notification of the decision. In the petition, the full details of the petitioner, the respondent and the subject of the objection must be mentioned precisely. In this article, we are trying to find out how and under what conditions the third objection (judgment, subpoena) occurs and to what extent it affects the litigation process. In this research, we have collected data and research resources using the library method.