Default in an agreement often occurs in the society. Default is negligence in carrying out obligations or not fulfilling the achievements as specified in the agreement between the creditor and the debtor. This research is intended to provide an explanation of the legal consequences of default on credit agreements using fiduciary collateral objects obtained unlawfully. This research is normative juridical research using conceptual approach, case approach, and statutory approach. The data collection was obtained from primary data in the form of legal materials and secondary data were taken from cases related to credit and fiduciary guarantees. The legal theory used as an analytical tool in this study is the theory of legal certainty, the theory of legal responsibility and the theory of dispute resolution. The results of this study show that legal consequence of a credit agreement that uses a fiduciary collateral object obtained illegally is that the guarantee object cannot be executed because the guarantee object does not belong to the debtor. In terms of agreement this type of agreement is not legitimate because creditors and debtors both of them have no legal standing as required by Article 1320 of the Civil Code.