Autism spectrum disorder (ASD) and intellectual disability (ID) are neurodevelopmental disorders with strong genetic components. Increasingly, research attention has focused on whether genetic factors conveying susceptibility for these conditions, also influence the risk of other health conditions, such as cancer. We examined the occurrence of hospital admissions and treatment/services for cancer in mothers of children with ASD with or without ID compared with other mothers. After linking Western Australian administrative health databases, we used Cox regression to estimate the hazard ratios (HRs) of any hospitalisations and treatment/services for cancer in these groups of mothers. Mothers of children with ASD without ID had greater risk of admissions for cancer (HR 1.29 [95% CI 1.1, 1.7]), and for treatment/services in particular (HR 1.41 [95% CI 1.0, 2.0]), than mothers of children with no ASD/ID, while mothers of children with ASD with ID were no more likely to have a cancer-related hospital admission than other mothers. Mothers of children with autism without ID had increased risk of cancer, which may relate to common genetic pathways.