Background: People with intellectual disabilities are at much higher risk of preventable deaths compared to the general community. However, studies identifying the cause of death in people with intellectual disability are generally based on one primary cause which is frequently attributed to the person's disability. Therefore, the aim of this study was to identify the most common associated causes that may have contributed to the deaths of Australians with intellectual or learning disabilities, particularly those that may be avoidable. Methods: Linked data that had previously been used to identify underlying causes of deaths were re-analysed to determine other contributing causes of death in Australians with intellectual disabilities aged under 65 years who accessed disability services between July 2013 and June 2018. Findings: Two thousand three hundred and thirty-three deaths occurred among 180,790 people with intellectual disability. Contributing causes of death with the greatest disparities compared to the general community were lung diseases due to external agents (adjusted rate ratio (RR) 70.6 (95% confidence interval [95% CI] 63.7-78.2), influenza and pneumonia (RR 18.3; 95% CI 16.4-20.4), and coronary heart disease (RR 3.3; 95% CI 2.8--3.8). Conclusions: Analysing all contributing causes of death in people with intellectual disabilities can ensure that the higher rates of preventable deaths in people with intellectual disability are identified and addressed earlier in the disability and health sectors.