The Transfer of debt in the Principles of European Contract Law is a tripartite agreement that may also be concluded between the original debtor and the new debtor. The existence of scattered provisions in Iranian law, especially assuming the formation between the transferor and the transferee, needs to be investigated by the present study with aim to eliminate the shortcomings in the law and with descriptive-analytical method. The results show there is a relationship between the transferor and the transferee in three ways. First, the contract. The transfer of debt, even if it is made between the transferor and the transferee, will lead to the full substitution of new debtor, provided that there is the prior consent of the creditor. In addition, the contract concluded between the transferor and the transferee without the consent of the creditor will lead to the transfer of debt with incomplete substitution of new debtor, like a liability insurance. Second, the existence of debt. Third, the area of responsibility transferred to the transferee. principle is to transfer the debt to the transferee with the same characteristics as the original debtor. However, the liability of debt transferee may increase or decrease, such as a liability insurance.