This mixed-methods study examined therapist self-disclosure (TSD) in 16 cases of naturalistic therapy to describe how real therapists use self-disclosure with real clients and to explore which characteristics of TSD contribute to its effectiveness. Judges coded 185 TSD events from 115 sessions of psychodynamic psychotherapy for type (facts, feelings, insight, strategy); whether disclosures were reassuring, challenging, both, or neither; intimacy level; quality level; and initiator. Relationships among these characteristics and clients' session outcome ratings (Real Relationship Inventory and Working Alliance Inventory) were examined using Hierarchical Linear Modeling. Likelihood of disclosure occurrence and certain disclosure types and characteristics were related to client post-session ratings of the real relationship and the working alliance. Higher-intimacy disclosures (moderately intimate) were associated with stronger client ratings of the real relationship and the working alliance. It is argued that therapist self- disclosure is multifaceted and complex. Implications for research, training, and practice are discussed.