This article presents an intensive study of the outcome and process of the psychotherapeutic treatments conducted at the Blanquerna Psychotherapy Service in Barcelona. It analyzes in detail the relation between outcome (improvement) and process (therapeutic alliance). Specifically, it discusses (a) the therapeutic process in terms of the relation between therapeutic alliance and psychotherapy outcome and (b) the effects of the temporary weakening of the therapeutic alliance and temporary symptomatic relapse on therapeutic outcome and process. Two hundred thirty-nine clients were included in the study, and the assessment instruments were the CORE Outcome Measure and the short version of the Working Alliance Inventory. In addition to good outcome of psychotherapy and maintenance of therapeutic change after treatment, the results also demonstrated the significance of different aspects of the therapeutic alliance as predictors of the therapeutic outcome and process.