The institution of third-party intervention in civil lawsuits is considered an important mechanism for ensuring the right to defense, preventing the violation of the rights of persons outside the proceedings, and preventing the issuance of conflicting decisions. Among the examples of this institution, third-party objection has a special place because it refers to a situation where a judicial decision, without the presence of the interested party in the proceedings, interferes with his right or legal claim. The present study aims to analyze the foundations, conditions, scope, and legal effects of third-party objection and examine its legislative and executive challenges in the Iranian civil procedure system. The main question of the study is to what extent the regulations governing third-party objection have established a balance between protecting third-party rights and the need to maintain the certainty and stability of judicial decisions. This study is applied in terms of purpose and descriptive-analytical in terms of method. The required information has also been collected and analyzed using library resources, legal documents, works of legal doctrine, and a review of judicially credentialed perspectives. The findings of the research show that the third-party objection, unlike the third-party entry and the third-party involvement that are raised during the proceedings, is a special objection method for a person who did not participate in the proceedings leading to the verdict as a litigant. According to Articles 417 to 425 of the Code of Civil Procedure, the realization of this objection requires the verification of two fundamental elements: first, the violation of the third-party's right as a result of the verdict; and second, the lack of interference by him or his legal representative in the proceedings leading to the issuance of that verdict. The results of the research also indicate that the third-party objection can be raised in two main and indirect formats, and the difference in the method of raising it, the hearing authority, and its connection to the ongoing litigation has important effects on the hearing process. Despite the supportive role of this institution, the ambiguity in the scope of objectionable decisions, the status of some judicial decisions, the lack of a clear time criterion for filing an objection, the difficulty in determining the competent authority in some cases of indirect objection, the possibility of delaying the proceedings, and possible abuse or collusion are considered to be its most important practical challenges. Therefore, reforming and clarifying the relevant regulations, explaining the precise criterion of "interference with the rights of a third party" and providing guarantees to prevent false objections, can increase the efficiency of this institution and create a more favorable balance between the right of defense of third parties and the principle of finality of decisions.