Trauma-focused psychological interventions for Ch-PTSD treatment are efficacious, however, an average dropout rate of 22.3% underscores the importance of identifying client factors predicting treatment success, enabling therapists to address these predictors during treatment, improve treatment outcomes, and reduce dropout rates. Two dysfunctional schema modes, the detached protector and the suspicious overcontroller, may be relevant for Ch-PTSD as they overlap with Ch-PTSD characteristics and, subsequently, influence the therapeutic alliance, which is one of the most robust predictors of psychological treatment success, and also a significant factor in Ch-PTSD treatment success. Therefore, this study investigated whether specific schema modes negatively predicted TA development during treatment, as tested by both therapists and patients, in a clinical sample of N = 199 adults with Ch-PTSD (aged 18-70) undergoing Imaginary rescripting and eye movement desensitization and reprocessing treatment once or twice weekly. Furthermore, the exploratory analysis examined to what extent patients and therapists reported similar TA development during treatment.