the caspian sea contains great resources of oil and gas. the caspian sea is a 700- mile- long body of water in central asia, land located between azerbaijan, iran, kazakhstan, russia and turkmenistan. iran was challenges and opportunities in the caspian region. key question in this thesis includes three section that first question, opportunities of iran in the caspian region, second question challenges of iran in the caspian region, third question is how to use these challenges and opportunities in the way of national interest. hypotheses divided to three section, first section includes opportunities of iran in the caspian region (resources of oil and gas, strategic_ geopolitical position of iran and the historical_ cultural similarities), second section includes challenges of iran in the caspian region (determination legal regime, environmental problems and influence of great powers), three section includes multilateral cooperation in the caspian region that help to iran in the way of national interest. in this research we don’t consider the historical_ cultural similarities of iran with littoral states of the caspian sea and the influence of great powers.