Today, along with globalization, we observe economic convergence in different parts of the world. In fact, closeness of culture, race, language, religion and etc. in countries of one region, along with shorter distances and less transportation costs, have led to greater will for more cooperation among these countries. In this paper, using a gravity model, the trend of bilateral trade between Iran and ECO countries is examined, and present convergence between Iran and these countries, both on the aggregate level and on the segregated sectors of different goods, is evaluated. Then, this convergence is compared with that of Iran and EURO countries. Empirical evidence shows that the bilateral trade pattern between Iran and its trade partners in ECO is a traditional one (traditional model) with an inter-industry trade structure. In addition, comparing the results of the convergence level between ECO and EURO countries shows that the rate between Iran and ECO countries is greater than that of Iran and EURO countries. The reasons can be attributed to the similar economic, social and religious structures of these countries. In addition, the results obtained from ten separated sectors show that Iran, due to superior quality of its goods, has a vertical intra- industrial trade with ECO countries in the 3 rd ,4th, 5th, 6th, 7th, 8th, 9th, and 10th groups of goods.