Locus of control has been implicated as an important construct that is related to treatment outcome for several groups of offenders, including sexual offenders. However, little attention has been paid to how this construct is related to sexual offending by people with intellectual disabilities. Given this, 41 participants with intellectual disabilities were recruited into three groups: sex offenders who had undergone psychological treatment, sex offenders who had no history of treatment, and nonoffenders. All participants completed measures of locus of control and distorted cognitions. There was a significant difference between those who had and had not completed treatment in terms of cognitive distortions relating to sexual offending. There was no significant difference between the three groups on the measure of locus of control, with all three groups endorsing an external locus of control. Three possible explanations for how locus of control relates to sexual offending by people with intellectual disabilities is explored and discussed.