Clinicians’ own internal resources for understanding relationships—that is, their attachment organizations—have been found to influence the process and outcome of treatment. The current study addressed whether the attachment organizations of novice couple and family therapists were associated with couples’ experiences of their therapists, therapeutic alliance, session impact, and emotionally focused couple therapy (EFT) fidelity (i.e., especially as related to targeting and working with attachment needs and overt and underlying emotions). Novice couple and family therapists delivered EFT, an attachment-based approach, to couples in a simulated session and an embedded multicase study design guided a cross-case analysis. Findings indicated that secure therapists, when compared to their insecure peers, were more competent at working with attachment needs, as well as the overt and underlying emotions of their clients. Secure therapists perceived themselves as being more skilled in emotion regulation, which may have contributed to their abilities to remain attuned to their clients’ attachment needs and emotional expression, even in the face of emotional arousal in session. Couples of insecure therapists also reported greater alliance splits. Future research is needed to further explore the dyadic influences of both therapists’ and clients’ attachment organizations, as well as the training and supervision practices these findings implicate.