This study aims to analyze the validity of a gift agreement made without the consent of the heirs concerning undivided inheritance property. The case study that serves as the focus of this research is the Supreme Court Review Decision Number 198 PK/Pdt/2019. The background of this research emphasizes the importance of understanding the validity of agreements that require the consent of all relevant parties regarding a specific object. The research method applied is normative-empirical legal research, which includes library studies and interviews, using a case study approach. In examining the validity of the gift agreement, Indonesia's positive law, as outlined in the Civil Code, serves as the primary reference. The findings indicate non-compliance with Article 1320 of the Civil Code regarding the legal requirements for a valid agreement: mutual consent, legal capacity, a specific object, and lawful cause. Additionally, the agreement does not meet the conditions for a valid gift as stated in Article 1666 of the Civil Code. The defendant and the plaintiffs’ mother made the gift agreement unilaterally without involving the consent of other heirs regarding undivided inheritance property. This action has harmed the rights and interests of the heirs. The urgency of this research lies in the frequent occurrence of unilaterally made gifts within families, bypassing the consent of other parties. If this phenomenon is left unaddressed, it can lead to the obstruction of rights to the property in question, trigger family disputes, and result in legal uncertainty regarding the status of the property. The study concludes that the gift agreement does not meet the validity requirements for agreements as stipulated in Article 1320 of the Civil Code. The agreement was annulled by the court, as there was no initial consent from all heirs.