The age difference between spouses can affect fertility, family planning, divorce, marital satisfaction, and widowhood. The age difference has relatively been higher in Ardabil province. Using Iran 2006 census data this paper has tried to show and explain the effects of social and demographic factors on the age difference among women aged 15-49 years in Ardabil province. The average age difference of couples was about 5 years and in about 80 percent of marriages women were younger than their husbands. Age, education, employment, place of residence, migration and remarriage had significant relationships with the dependent variable. The relationships can be explained by social, economic and demographic changes.