Introduction: Symptom assessment is key to managing symptom burden following a cancer diagnosis. People with IDD receive inequitable health care and experience worse outcomes from cancer; disparities may also exist in routine cancer symptom screening. In this study, we investigated whether differences exist in cancer symptom assessment between people with and without IDD. Methods: We conducted a matched retrospective cohort of adults in Ontario with and without IDD who received a cancer diagnosis between 2010-2019 using administrative health data at ICES. Individuals were followed until 30/9/2021. Among people with cancer, those with IDD were hard-matched 1:5 to those without IDD on age at diagnosis, sex, diagnosis year, cancer type, and regional cancer centre registration. Cumulative incidence of first symptom assessment accounting for death as a competing risk was estimated. Subdistribution and cause-specific hazard models were used. Effect modification by cancer stage was investigated. Results:1545 people with IDD were matched to 7,725 people without IDD. Individuals with IDD experienced a lower incidence of cancer symptom assessment (1-year probability: 0.62 vs. 0.77). People with IDD had lesser rates of symptom assessment (subdistribution HR: 0.63, 95% CI: 0.59,0.67) (cause-specific HR: 0.69, 95% CI: 0.65,0.73) relative to those without IDD. Results were consistent across cancer stages. Discussion: The incidence of cancer symptom assessment is lower among cancer patients with IDD compared to those without. These findings may indicate poor usability of the symptom screening tool; language and readability checks should be conducted to enhance accessibility of this tool.