Locus of control can be a useful measure of treatment outcome in offenders from the general population. However, there is little information regarding locus of control and offenders with learning disabilities. Existing measures of locus of control use complex language and abstract ideas that may not be accessible to individuals in this group. A new 20-item measure, using written statements and cartoons, was developed. The tool was then used to compare locus of control in offenders and alleged offenders (n = 41) and non-offenders (n = 61) with learning disabilities. A significant relationship was found between locus of control and offender status if the offender was convicted (n = 22). Where there was offending behaviour but no conviction (n = 19), there was no significant difference between this group and the non-offender sample. Convicted offenders with intellectual disabilities appear more likely to have a greater external locus of control than alleged or non-offenders. The new locus of control scale may be a useful measure of treatment outcome in offenders with learning disabilities.