One of the main concerns that many countries of the world are encountering, is some economic activities which are usually hidden from official view. Activities such as exchanging stolen goods, drug trafficking, corruption, gambling, smuggling, are among illegal activities, and others like refusing to report the incomes, fringe benefits, and cash discounts for the staff are among the legal activities of shadow economy. A considerable part of economic literature during the past decade focused on the research findings concering the ways of measuring, defining, and determing the extense of shadow economy in the world. Using the “Structural Equation Modeling” and some literature-specified causes and indicators we aim to reach the case study of Iran. Estimation of size and evolution of Iranian shadow economy is analyzed through “Dynamic Multiple Indicators-Multiple Causes” which is one of the most important indirect techniques available. The advantage of this model is evaluation of the simultaneous impacts of all variables on each other, and has fewer restrictions compered to other models. The research findings reveal the increasing trend of shadow economy in Iran and acts as an alarm for policy makers and authorities.