Purpose: To evaluate the usefulness of asenapine sublingual tablets for the treatment of delirium in patients with advanced cancer. Methods: We conducted a retrospective study using electronic medical records of patients with advanced cancer who were admitted to our hospital between October 1, 2019 and September 30, 2022 and who received asenapine sublingual tablets as treatment for delirium. The Agitation Distress Scale (ADS) was used to evaluate the degree of improvement of agitation symptoms caused by delirium. Results: Twenty patients were included in the analysis. The mean ADS(range) before treatment was 12 (4–17), and the mean ADS(range) after treatment was 7.9 (0–18), with the p-value <0.001. Conclusion: Asenapine sublingual tablets may be useful as an option for pharmacological treatment of delirium.