We report a first randomized clinical trial examining the effect of immediate and non-immediate therapist self-disclosure in the context of a brief integrative psychotherapy for mild to moderate distress. A total of 86 patients with mild to moderate forms of distress were randomly divided into three 12-session integrative psychotherapy conditions based primarily on [Hill, C. E. (2009). Helping skills: Facilitating, exploration, insight, and action (3rd ed.). Washington, DC: American Psychological Association.] three-stage model. Therapists trained in this treatment modality were instructed to use either immediate self-disclosure (expressing feelings towards the patient/treatment/therapeutic relationship) or non-immediate self-disclosure (expressing personal or factual information regarding the therapist's life outside the treatment). In the comparison condition, the therapists were instructed to refrain from self-disclosure altogether. Immediate therapist self-disclosure reduced psychiatric symptoms among patients with elevated pretreatment symptoms (as assessed by the Brief Symptoms Inventory) and bolstered a favorable perception of the therapist. Therapists in both the immediate and non-immediate self-disclosure group evaluated themselves more favorably than their counterparts in the non-disclosure group. Therapist self-disclosure, particularly of the immediate type, might enhance the effect of brief integrative treatment on psychiatric symptoms of high symptomatic patients and contribute to favorable perception of therapists.