Baitul Maal wat Tamwil (BMT) as a financial institutionin Indonesia must compliance to the Islamic law, namely Fatwa Dewan Syariah Nasional Majelis Ulama Indonesia (DSN-MUI). But in reality shows the opposite. One of the causes is the lack of consciousness the laws of society. This empirical research wants to find out how customers of BMT in Tongas Probolinggo understanding against mudharabah contract. Research is done by approach juridical antropologis. Lack of understanding of the customer against the mudharabah contract mis-information by the BMT. Besides, experience customers factors associated with financial institutions formerly also affect. Mudharabah contract still understood as the loan with the obligation of paying interest, not as a result of ratio a share of the revenue. Collateral in mudharabah contract is also seen as a matter a reasonable. However, the understanding BMT's customers to the values of contract, namely trust, justice, honesty, and mutually beneficial, are good in general. This can not be separated from the influence of social and cultural of the locations of this research.