This was a cross-sectional and retrospective study of the short-term effects of the COVID-19 pandemic among patients with colorectal or anal cancer treated at AA Camargo Cancer Centre, a large and comprehensive cancer centre located in Sao Paulo, the epicentre of the pandemic in Brazil. The aim was to quantify the barriers to access to treatment and diagnosis of these tumours during the pandemic in comparison with the previous year. The results showed a significant decrease in newly diagnosed patients with colorectal or anal cancer, a significant increase in patients with locally advanced disease at presentation, and an increase in the proportion of patients without insurance for coverage of costs.