As a result of demographic transition, the age structure of the population of Iran, in general, and those in marriageable ages, in particular, has changed during the past few decades. Concomitant changes in marriage raise the question that whether these two phenomena are related. Using the published results of the 1966-2011 Iranian censuses, this paper studies the impact of the dynamics of the population age structure on changes in marriage at the national and rural-urban levels. The standardization technique is applied to determine the proportion of never-married men and women after controlling for changes in the age structure of the population during different time periods and across successive birth cohorts. The findings suggest that the similarity of age structure cannot remove either period or cohort marriage differences. Thus, recent changes in the marriage timing should be sought in factors other than changes in the age structure of the population.