Background: Ticagrelor monotherapy after 3 months dual antiplatelet therapy (DAPT) with aspirin and ticagrelor can reduce bleeding without increasing ischemic events after percutaneous coronary intervention (PCI). However, the impact of this approach among the patient with diabetes remains unknown. Methods: This was a sub-analysis of the Ticagrelor Monotherapy after 3 months in the Patients Treated with New Generation Sirolimus Eluting Stent for Acute Coronary Syndrome (TICO) trial. After successful PCI, the patients were randomly assigned to ticagrelor monotherapy after 3-months DPAT or to ticagrelor-based 12-months DAPT. We compared ischemic events and bleeding events between the patients with diabetes and without diabetes for 12 months. Ischemic events were defined as death, myocardial infarction, ischemic stroke, transient ischemic attack, stent thrombosis, and any revascularizations. Bleeding events were defined according to the Thrombolysis in Myocardial Infarction (TIMI) criteria and Bleeding Academic Research Consortium (BARC) definition. Results: Between August 2015 and October 2018, 3,056 patients were enrolled in the TICO trial, of which 835 (27.3%) had diabetes mellitus. Diabetes mellitus was associated with all evaluated ischemic and bleeding events. No significant differences in any ischemic events were observed in patients with diabetes between ticagrelor monotherapy after 3-months DAPT and ticagrelor-based 12-months DAPT (hazard ratio [HR] 0.83, 95% confidence interval [CI] 0.45–1.52, p = 0.540). In patients with diabetes, the overall incidence of bleeding complications during the 12-months follow-up period did not differ between the two treatment groups (HR 0.83, 95% CI 1.48–1.43, p = 0.505). However, ticagrelor monotherapy was significantly reduced both any TIMI bleeding and BARC three or five bleeding events in diabetes patients in the 3-months landmark analysis, after 3-months DAPT period (HR 0.20, 95% CI 0.07–0.59, p = 0.003). Conclusion: In diabetic patients, ticagrelor monotherapy showed a lower incidence of bleeding complications after 3-months DAPT period, without increasing ischemic complications, compared with ticagrelor-based 12-months DAPT (ClinicalTrials.gov Identifier: NCT02494895).