Increasingly, researchers have operationalized Adult Attachment Interview (AAI)-derived attachment representations as reflecting individual differences in secure base script knowledge (AAIsbs) – the degree to which individuals show awareness of the temporal-causal schema that summarizes the basic features of seeking and receiving effective support from caregivers when in distress. In a series of pre-registered analyses, we used AAI transcripts recently re-coded for AAIsbs and leveraged a new follow-up assessment of the NICHD Study of Early Child Care and Youth Development cohort at around age 30 years (479 currently partnered participants; 59% female; 82% White/non-Hispanic) to assess and compare the links between AAIsbs and traditional AAI coding measures at around age 18 years and self-reported romantic relationship quality in adulthood. Higher AAIsbs predicted better dyadic adjustment scores in adulthood (r = 0.17) and this association remained significant controlling for other AAI-derived coding measures, as well as sociodemographic and cognitive functioning covariates. Findings extend previous evidence pointing to the predictive significance of AAIsbs for multiple adult functioning domains.