The relationship that develops between a client and therapist is arguably one of the most important factors toward achieving positive outcomes from therapy. The present study examined the therapeutic alliance, as measured by Horvath and Greenberg’s Working Alliance Inventory (WAI), as a function of Aboriginal ancestry and the relationship of alliance to important program outcomes, in a Canadian correctional sample of 423 treated sexual offenders. The men rated their primary therapists on the WAI 3 months into treatment. Higher self-report ratings on the WAI and its Task, Bond, and Goal subscales were associated with lower rates of treatment non-completion and longer stay in treatment. Aboriginal men scored significantly lower on the WAI’s Bond subscale (i.e., the emotional connection between client and therapist) than non-Aboriginal men, although by and large, the offender sample as a whole otherwise registered fairly high mean scores on the tool. Aboriginal men scoring below the median on WAI total score had the highest rates of treatment non-completion. WAI total score and scores on the three subscales were unrelated to post-program recidivism in the community. Cultural implications for correctional client engagement and service delivery within the context of the risk-needs-responsivity model are discussed.