Attachment theory has been proposed as a suitable framework within which to understand and explore the therapeutic alliance. This review systematically explores research that has examined the relationship between clients' self reported attachment patterns and the therapeutic alliance. Methodological characteristics and study findings are reviewed and discussed with the aim of concluding whether assessing clients' attachment patterns would be beneficial to therapy. In spite of inconsistencies with regards to the measurement and conceptualisation of attachment and the alliance, the evidence suggests that clients who rate themselves as having a more secure attachment pattern are likely to rate the alliance as stronger. The implications of this for therapeutic practice are discussed.