This article examines the participation of the middle class in the Iranian Islamic Revolution from the perspective of the sociological approach to political participation and using a historical method. It addresses the question of why, in 1979, the middle class (both traditional and modern) played the most significant role in the regime change (revolution) in Iran. Based on a model of civic voluntarism, it offers three answers: First, the existence of sufficient motivation among members of this class; second, possession of the necessary abilities and resources (including time, financial capital, and civic skills) that facilitated participation compared to other classes; and third, encouragement or compulsion to participate through membership in political and social groups and networks. In other words, membership in these groups and networks played a significant role in encouraging and mobilizing members of the middle class to participate. It is evident that these three factors (sufficient motivation, necessary resources, and membership in social and political networks) were facilitated by the socio-economic base of these classes (including level of education, income level, and occupational status).