Should a dispute between a bank and its customer occurs, a mediation attempt is an alternative offered by Bank of Indonesia. This agreement is regulated by Bank of Indonesia Regulation Number 8/5/PBI/2006, dated 30 January, 2006 regarding Banking Mediation is done through agreement document. When preparing this document, the following principles of contract law should be prioritized: concensus, commitment (pacta sunt servanda), freedom to prepare a contract, good will, morality and prudential principles. Principles of contract law are the based to obtain a solution that fulfill the fairness for both parties.