Abstract Background and Hypothesis People with psychotic disorders have a higher risk of mortality following cancer diagnosis, compared to people without psychosis. The extent to which this disparity is influenced by differences in cancer-related treatment is currently unknown. We hypothesized that, following a cancer diagnosis, people with psychotic disorders were less likely to receive treatment and were at higher risk of death than those without psychosis. Study Design We constructed a retrospective cohort of cases of non-affective psychotic disorder (NAPD) and a general population comparison group, using Ontario Health (OH) administrative data. We identified cases of all cancers diagnosed between 1995 and 2019 and obtained information on cancer-related treatment and mortality. Cox proportional hazards models were used to compare the probability of having a consultation with an oncologist and receiving cancer-related treatment, adjusting for tumor site and stage. We also compared the rate of all-cause and cancer-related mortality between the two groups, adjusting for tumor site. Study Results Our analytic sample included 24 944 people diagnosed with any cancer. People with NAPD were less likely to receive treatment than people without psychosis (HR = 0.87, 95% CI = 0.82, 0.91). In addition, people with NAPD had a greater risk of death from any cause (HR = 1.68, 95% CI = 1.60, 1.76), compared to people without NAPD. Conclusions The lower likelihood of receiving cancer treatment reflects disparities in accessing cancer care for people with psychotic disorders, which may partially explain the higher mortality risk following cancer diagnosis. Future research should explore mediating factors in this relationship to identify targets for reducing health disparities.