Objective: In recent years, the Syrian crisis has been one of the most important international issues and has attracted the attention of many countries around the world. Syria has become an area of cooperation and competition between some regional and international powers. Meanwhile, the Islamic Republic of Iran and Russia have been the main influential actors in Syria. Tehran and Moscow, for some reason, are on the same front, working together to support the Syrian regime. On the other hand, the two countries have fields of conflict in Syria that affect their cooperation. Therefore, the main purpose of this study is to investigate the areas of cooperation and differences between Iran and Russia in the Syrian crisis. Methods: The method used in this study is descriptive-analytical and uses the theoretical framework of structural realism to analyze the areas of cooperation and difference between the two countries. Result: Mutual needs and international and regional requirements underpin Iran-Russia security cooperation are common to address security threats. On the other hand, the two countries' approach to the process of political settlement and the structure of the Syrian government in post-conflict conditions and their efforts for greater role-playing and influence, and the type of relationship they have with other actors involved in Syria, are areas of dispute between the two countries. Conclusion: Cooperation between the Islamic Republic of Iran and Russia in the Syrian crisis is tactical. They have been working together because of the cross-cutting needs, so in the long run the weakening of cooperation will make the differences between the two countries more pronounced, but due to some constraints a minimal level of cooperation between them will be maintained.