The present study examined the relationship between adult attachment style and therapeutic alliance in individual psychotherapy. Search procedures yielded 17 independent samples (total N = 886, average n = 52, standard deviation = 24) for inclusion in the meta-analysis. Results indicated that greater attachment security was associated with stronger therapeutic alliances, whereas greater attachment insecurity was associated with weaker therapeutic alliances, with an overall weighted effect size of r = .17, p < .001 (95% confidence interval = .10-.23). Publication bias analyses did not indicate any cause for concern regarding the results. The data were not demonstrably heterogeneous (Q = 6.10, df = 16, p = .99), and all between-study moderator analyses were nonsignificant (p values > .10) with the exception of the source of alliance ratings; results indicated that patient-rated alliance demonstrated a significantly larger relationship with attachment compared with therapist-rated alliance (Qbetween = 3.95, df = 1, p = .047). Implications for clinical practice and future research are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved).