Research and theoretical models have consistently identified sexual interest in children as a key factor involved in child sexual offending. However, there is only moderate agreement in the diagnosis of pedophilia and different assessment methods identify different offenders as pedophiles. The current study examined the discriminative and convergent validity of three different measures of sexual interest in children. Participants included sex offenders and nonsex offenders recruited from federal prisons (i.e., offenders serving sentences of more than 2 years) in Ontario, Canada. Child molesters’ responses (n = 35) were not significantly different from nonsex offenders (n = 21) on an implicit measure of sexual interest in children (Sexual Attraction to Children Implicit Association Test [SAC-IAT] d = 0.44, 95% CI [–0.11, 0.99]), but differed on the self-report (Sexual Interest Profiling System; d = 0.83, 95% CI [0.27, 1.39]) and viewing time (d = 1.15, 95% CI [0.54, 1.75]) measures. Findings did not provide clear support for the superiority of a multimodal approach, possibly due to the relatively small sample. More often than not, convergence between the three measures was observed (n = 74). Findings from the present study are an important step toward understanding the relationship between different measures of sexual interest in children and establishing their validity.