The current study examined associations between attachment/relational variables in waking life and in sleep mentation (dream content). The general prediction was that individuals in dating relationships would have dreams about romantic partners and relational situations that reflected the dynamics of their relationships in waking life, arising from personal feelings of security as well as interactions with romantic partners on specific days. Sixty-one young adults in committed dating relationships participated in the study. Participants completed measures of attachment, relationship interdependence, and closeness, followed by a two-week daily diary of dream reports and their interactions with romantic partners each day. Participants reported on emotions felt in dreams (e.g., joy, anger, jealousy) and blind coders scored dreams for secure base content and relational scenarios (e.g., dating, infidelity). The main hypotheses were supported: secure attachment scores correlated with richer secure base content in dreams. Furthermore, attachment interacted with daily love, conflict, and general interaction with romantic partners, such that secure people experienced more general positive emotion (e.g., joy) and less general negative emotion (e.g., anger) in dreams containing romantic partners depending on their daily activity. In contrast, dreams containing higher jealousy or guilt, as well as scenarios involving a partner's infidelity did not vary by daily feelings; they were driven solely as a function of dispositional insecurity. Interdependence was associated with lower likelihood of dreams involving alternative (extra-dyadic) partners following increased daily conflict, and higher likelihood of dreams involving marriage. Jealous emotion in dreams and dreams containing behavioral conflicts each predicted increased conflict with romantic partners the following day. Dreams involving infidelity predicted less love felt the following day, and any dream involving romantic partners produced less love and more conflict on the following day for individuals high in anxious attachment. The findings illuminate understanding of attachment mental representations and relationship interdependence, displaying how relational schemata manifest in dream content, and how dream affect/content influences people's post-dreaming behavior.