Educational homogamy, or similarity of couples in terms of educational attainment, is one of the important aspects of mate selection, which, due to its social, economic, and emotional consequences, has centered the attention of many researchers around the world. Yet, no information regarding changes in educational homogamy and its levels in Iran is available. Using individual data from the 2% sample of the 2006 Iranian census, this paper examines four decades of change in the similarity of couples in terms of educational attainment. Specifically, changes in the general trend of educational homogamy as well as the specific pattern of homogamy in each level of education are examined for women born between 1940 and 1980. The findings suggest that the level of educational homogamy for these cohorts has reduced from 75% to 48%. In contrast, the proportion of women marrying husbands with lower educational attainment has increased from 4% to 24%. It seems that the fall in educational homogamy in Iran has corresponded with a rise in the share of higher educated women marrying men with lower education. In addition, the examination of changes in educational homogamy by the level of education shows an increase in homogamy in the intermediate levels and a decline in the upper and lower levels.