With a growth rate higher than global GDP, exports, etc., Marine business (especially container transport) has had great effects on the spatial structure of different regions and areas. Ports have an important role in this regard, because they are the main gates of goods import and export in a country. This study explores the structure and interconnection of Iran’s northern ports (on Caspian  Sea) with the ports of other countries neighboring Caspian  Sea due to the great importance of marine transportation and its effectiveness on Iran’s spatial structure interconnection. In order to examine the evolution of the spatial interconnection network structure of Iran’s northern ports at local and international level between the years 1989 to 2019, the model used in this study analyzed the passenger and goods transportation among Caspian  Sea ports of Iran and those of other countries around Caspian  Sea using UCINET software. The results showed that the interconnection of goods and passenger transportation in Iran’s northern provinces (in general) and Iran’s ports on Caspian  Sea (in particular) is not in good conditions. In fact, the connection between Iran and other countries neighboring Caspian  Sea is not so high except for scarce, insignificant cases (i.e., connection with Russia through Amirabad port), and the spatial interconnection of other borders of Iran, especially the southern coastline, is much higher than that of Caspian  Sea coastline.