Individuals with unresolved/disorganized representations of childhood trauma (U/d attachment) report more psychological distress than others, but little is known about their everyday mentation. In the present study adults with childhood trauma (N = 45) completed the Berkeley-Leiden Adult Attachment Questionnaire-Unresolved (BLAAQ-U) and the Adult Attachment Interview (AAI), and reported everyday mentation during 5 days of experience sampling. The BLAAQ-U and the AAI showed a medium association with each other, but only the former significantly predicted negative affect, dissociation, and low control/awareness of mentation. Contrary to our predictions, U/d attachment did not significantly predict mind wandering, but the BLAAQ-U predicted endorsements of a negative mind wandering style. U/d attachment, as assessed by both instruments, was associated with the Poor attentional control style and beliefs in anomalous mental phenomena. Experience sampling is a valuable way to investigate everyday experiences in individuals with U/d attachment.