This longitudinal population-based study aimed to investigate the prospective relationship between PTSD symptoms following childbirth and prenatal attachment in the subsequent pregnancy. Data were derived from the Norwegian Akershus Birth Cohort (ABC), a large population-based prospective cohort study. Data from 1473 women who had given birth at least once before and who had completed questionnaires at 17 and 32 weeks of gestation were included. Confirmatory factor analysis of the short version of the Prenatal Attachment Inventory was conducted to validate the scale. Further, structural equation modeling techniques were used to estimate prospective associations of PTSD symptoms following childbirth with prenatal attachment. Finally, to explore potential mechanisms of the association, mediation and moderation analyses were conducted. PTSD symptoms following previous childbirth were found to be prospectively related to higher levels of prenatal attachment in the subsequent pregnancy, while controlling for important confounding factors, such as symptoms of maternal depression and anxiety, previous pregnancy loss, and sociodemographic factors (maternal age, educational level, marital status, and number of children). When fear of childbirth was included as a potential mediating variable, the prospective relationship between PTSD symptoms following childbirth and prenatal attachment in the subsequent pregnancy increased, thereby indicating a suppressor effect. Fear of childbirth did not act as a significant moderator. Our findings suggest that a subsequent pregnancy following a traumatic childbirth may for some women represent an opportunity for a higher level of prenatal attachment, whereas high levels of fear of childbirth may be detrimental for prenatal attachment.