When there is an ambiguous contract, it must be interpreted.For the purpose of correct interpretation of a contract, it is necessary to observe some rules and principles among which is ' Contra Proferentem Rule'. If the drafter (creator) of a contract also was the obligee of it or the composition of a contract (or clause) wasn' t related to one of the parties, in this case the mentioned rule to be used in the concept of ' preference of interpretation against obligee'. But if one of the parties draft the contract (a clause of it) and the other party accept it, in this case the ambiguity of the contract will be interpreted against the drafter (composer) whether he is the obligee or not. So in such a case, interpretation against the drafter will be superior to the interpretation against the obligee. Since the.issue has not attracted much attention in Iranian Law, this article will have it as the central point of study. Also the contra proferentem rule, in line with the protection of consumer rights, is to be used in the intrpretationof non-responsibility clauses in order to give them their proper and just sense.