This study aims to analyze and find the current implementation of post-nuptial marriage agreements, to analyze and find the legal standing of marriage agreements made after marriage to third parties (Post-Decision of the Constitutional Court Number. 69/PUU-XIII/2015), to find reconstruction the validity of the marriage agreement after marriage. This research is included in the socio-legal research tradition. Socio-legal research examines the application of legal principles or norms by using legal and social science approaches. Weaknesses in the implementation of the post-nuptial agreement at this time are the weakness in the absence of post-nuptial agreement arrangements, the weakness that there are opportunities for misuse of the situation by the parties in the post-wedding agreement; as well as the weakness in the form of a culture of society that only realizes the importance of the marriage agreement after the marriage takes place. The reconstruction carried out is to add Article 185A of the Civil Code which states that the provisions referred to in Article 155 to Article 185 also apply to marriage agreements made after and in marriage.