This paper reports on changing policy direction of the Islamic Republic on family size and family planning in Iran. We discuss early state intervention policies in the 1920s, and its intensification with the establishment of family planning program in 1960s. The establishment of an Islamic Republic produced a strong 'hands-off' approach and lack of support for family planning and birth control. Economic realities of a fast growing population, compelled adoption of a comprehensive family planning program in 1990s, which contributed to the decline of family size by 2000. While pragmatic family planning and the provision of services can explain some of this decline in family size, a major question remains as to what were the factors influencing the motivation for adoption of family planning by couples and their desire for having less children. We allude to the diffusion of economic aspiration, and how child-centered family orientation contributed to the overwhelming acceptance of the family planning program in Iran in the last decade.