There is a need for appropriate screening tools for the assessment of autism spectrum disorder (ASD) in those with learning disabilities (LD) given the co-occurrence of the two conditions. The AQ-10 is the screening tool recommended by NICE (2012) for the case identification of ASD in adults with a borderline or mild learning disability. However, the AQ-10 was not developed with this population in mind. A mixed-methods approach was used to investigate the utility of the AQ-10 in its original form as a case identification tool. The AQ-10 was then redesigned and piloted. Qualitative results revealed individuals found the AQ-10 too inaccessible in its current format. Following revision, the diagnostic validity of the revised measure (AQ-10-R) showed good sensitivity (0.85) and specificity (0.77), whereas the diagnostic validity of the original AQ-10 was poor. The internal consistency for the AQ-10-R was 0.67 and 0.30 for the AQ-10. These findings indicate that simple formatting and administration changes may be needed to the AQ-10 before clinicians consider using it when helping to make decisions regarding referral for diagnostic assessment in those with borderline or mild learning disabilities.