The marriage agreement after the Constitutional Court Decision Number 69/PUU/XII/2015 has a slight difference from the initial concept regarding the marriage agreement. The pre-nuptial agreement which was later extended to the post-nuptial agreement basically had several issues, especially regarding the publicity of the marriage agreement. The enforceability of a post-nuptial agreement in certain conditions may create uncertainty for third parties regarding the husband and wife's assets. Based on these legal issues, this research aim to find out the formulation of the principle of publicity in the arrangement of the marriage agreement during the marriage (Post Nuptial Agreement) so that it can have binding power to provide legal protection for third parties. This study uses a normative juridical method, which is a process to find and study doctrines, principles and legal rules as an effort to answer the legal issues under study. There are five approaches used, including: a statutory approach (statute approach) by reviewing the Burgerlijk Wetboek, the Law on Marriage and its amendments, the Law on the Position of Notary Public and its amendments and related implementing regulations; conceptual approach (conceptual approach), namely exploring various expert opinions regarding the concept of agreement, the concept of marriage, the principles of marriage law, the concept of marriage agreements, the theory of legal protection, the theory of justice, the principle of balance, the principle of freedom of contract to the position of a third party in the agreement; historical approach (historical recht approach) aims to study the history of the enactment of laws and regulations that have been in force, especially those relating to marriage agreements, in addition to reviewing the treatise on the formation and legal politics regarding the Marriage Law and treatises on marriage agreements in effect in Indonesia; case approach, namely Constitutional Court Decision Number 69/PUU-XIII/2015 and Supreme Court Decision Number 598 PK/Pdt/2016; comparative approach, namely the Netherlands, the United States and Australia.
 KEYWORDS: Marriage Agreement, Principle of Publicity, Third Parties