Performance of contract in many situations is not possible without cooperation from the side of the obligee, and he/she has a duty to do all acts which are necessary to make enable the obligor for contract performance. For example, the execution of medical contract depends on patient’s cooperation. All items of such duty are not capable to cite in different kinds of contracts and in some cases they depend on conditions of contract and surrounding circumstances. The important basis of cooperation duty is good faith principle, but implied terms and customs are other essentials of this duty.
In Iranian legal literature, duty to cooperate is not considered neither by legislator, nor authors and jurisprudence, but in some legal systems and international instruments it is related to contracts such as UPICC, PECL, DCFR and OHADA where the principles are confirmed and the remedies of breach of such duty are determined. We studied in this article the concept, basis, scope and effects of cooperation duty in this article by carrying out comparative analyses.