Afghanistan is a patrilocal, patrilineal society in which women have limited societal participation. Such characteristics are often found in societies expressing a preference for sons. Despite a vast literature on the preferred sex composition of children in various nations, limited research has been conducted in Afghanistan because of security concerns and scant quantitative data. Our analysis focuses on couples’ willingness to shorten birth intervals and the desire to continue childbearing to obtain the desired sex composition of children. Using the 2015–2016 Demographic and Health Survey, we calculate parity progression ratios and estimate logit models explaining the prevalence of short birth-to-conception intervals, controlling for the sex composition of older siblings. Our findings are mixed, showing that Afghan couples desire to have children of both sexes and, at the same time, to secure a son rapidly.