AIMS: People with severe mental illness (SMI) have a greater risk of dying from colorectal cancer (CRC), even though the incidence is lower or similar to that of the general population This pattern is unlikely to be solely explained by lifestyle factors, while the role of differences in cancer healthcare access or treatment is uncertain. METHODS: We undertook a systematic review and meta-analysis on access to guideline-appropriate care following CRC diagnosis in people with SMI including the receipt of surgery, chemo- or radiotherapy. We searched for full-text articles indexed by PubMed, EMBASE, PsychInfo and CINAHL that compared CRC treatment in those with and without pre-existing SMI (schizophrenia, schizoaffective, bipolar and major affective disorders). Designs included cohort or population-based case-control designs. RESULTS: There were ten studies (sample size = 3501-591 561). People with SMI had a reduced likelihood of surgery (RR = 0.90, 95% CI 0.92-0.97; p = 0.005; k = 4). Meta-analyses were not possible for the other outcomes but in results from individual studies, people with SMI were less likely to receive radiotherapy, chemotherapy or sphincter-sparing procedures. The disparity in care was greatest for those who had been psychiatric inpatients. CONCLUSIONS: People with SMI, including both psychotic and affective disorders, receive less CRC care than the general population. This might contribute to higher case-fatality rates for an illness where the incidence is no higher than that of the general population. The reasons for this require further investigation, as does the extent to which differences in treatment access or quality contribute to excess CRC mortality in people with SMI.