This study investigates the relationship between engagement, denial, and treatment progress among a sample of 61 male sex offenders in outpatient group therapy. Three hypotheses were posed: (1) that denial is inversely related to engagement in group therapy; (2) that denial is inversely related to treatment progress, and (3) that engagement is correlated with treatment progress. Results revealed a strong correlation between engagement in group therapy, measured by the Group Engagement Measure, and sex offender treatment progress, assessed by the Sex Offender Treatment Rating Scale. Denial, measured by the Facets of Sexual Offender Denial Scale, demonstrated a strong inverse relationship to treatment progress. Engagement and denial were also strongly inversely related. Together, engagement and denial explained a significant amount of the variance in treatment progress. The findings provide support for current standards of practice that maintain that admitting to a sex crime is a necessary condition for progress and engagement in treatment. Strategies for increasing engagement and treatment progress, and reducing denial, are discussed.