This study uses innovative data from online dating to analyze men’s and women’s preferences regarding the age of a partner. These data include observations on how individuals behaved on online dating platforms as well as information on which preferences individuals stated in a survey from an online panel. The paper analyzes how male and female age preferences can be explained by an individual’s own age, preferences for other traits, and own market-relevant traits that are favorable or unfavorable for others. Our results show that age preferences essentially shift with age, but in different ways for men and women: Whereas men increasingly prefer younger women as they age, women’s age preferences become increasingly diverse. They also show that age preferences are confounded with gender-specific preferences for attractiveness and education. Finally, preferences for age also vary with marketrelevant traits such as education and parenthood, but not with prior marital experience. Altogether, our analyses point to a gender-specific decline in mate value with differential consequences for men’s and women’s mating preferences.