Women's labor force participation rate in Iran, compared to many other countries, is low. Using the country's census data, this paper aims to explore the changes in women's labor force participation during 1976-2011 and examine its relationships with main socio-demographic factors. Findings show that women's labor force participation, with upward and downward fluctuations, has decreased from 13.5% in 1976 to 11.5% in 2011. Social factors (like level of education), compared to demographic factors (like marital status and fertility), had stronger effects on labor force participation. The participation rate for women with tertiary education was much higher than that for their counterparts with a lower (secondary and less) level of education. Such low total labor force participation is mainly due to the large number of women who had no university education. The effect of marriage and the number of children, however, was negative. It seems that due to the increasing number of women participating in the labor market, the increasing number of women with university education, higher unemployment for women (especially for more educated women), and a lack of demand from the labor market, any improvements in women's labor force participation would encounter many barriers. The situation would have various implications for different components of sustainable development.