Changes in the individual's attachment orientation toward greater security are considered an important clinical goal. One promising underlying process of change in attachment orientation is shifting the emotion regulation tendency, in which the individual progresses from overreliance on the self or on the other to regulate emotional arousal. The present study utilized a computational approach to study shifts in the emotion regulation tendency as these manifest in the patient's and therapist's vocally encoded emotional arousal. The study examined whether shifts in the regulation tendency are associated with decreases in the level of insecure attachment and in strengthening of the therapeutic alliance. Shifts in the regulation tendency were examined throughout the early stages of treatment (Sessions 1-4) using 11,710 talk turns within 52 patient-therapist dyads. Findings suggest that shifts in the emotion regulation tendency are associated with greater strengthening of the therapeutic alliance and a decrease in the level of attachment avoidance. (PsycInfo Database Record (c) 2024 APA, all rights reserved).