Premarital sex is normatively unacceptable in Afghanistan, yet rapid social and cultural transformation in the country may be changing these traditional norms. In dialogue with cross-national scholarship, we examine attitudes toward premarital sex and experience of premarital sexual behaviours among urban Afghan youth. We use data from 1256 never married individuals aged 15-29 surveyed in ten Afghan cities. The results show that respondents, on average, have moderately liberal attitudes toward premarital sex and that almost one quarter of them had engaged in either sexual foreplay or penetrative intercourse. Multivariable results indicate that premarital sexual attitudes and behaviours were significantly associated with several individual-level characteristics, family and intergenerational relationships, and social ties and interactions. At the same time, instructive gender variations emerge. The findings illustrate the dynamics of premarital sexual relations in this and similar contexts where such relations are traditionally stigmatised but multifaceted, societal changes increasingly challenge this stigma.