Criminal's overall understanding of the concept of intention and his general interpretation in this field is one of the important challenges of the Islamic Penal Code in the field of criminal responsibility. The purpose of the  article is to investigate this important question, what is the effect of intention on criminal responsibility? The following article is descriptive and analytical and the subject has been investigated using a library method. Findings it showed that it is necessary to prove the existence of intention in all crimes, whether intentional or unintentional. The basis of criminal responsibility is the voluntariness of the behavior. If a person do not have the right to freely choose his own behavior, which means that he lacks freedom of intention or there is no opportunity for him to choose his behavior, then he cannot be held criminally responsible. In the analysis of the role of intention in the realization of criminal responsibility in Iranian law, it should be said that the Mens Rea is the cornerstone of every crime and until the criminal thought of the perpetrator is analyzed, intention cannot violate the law. The intention is an invisible thing and it must always be a intention to commit a crime.