Objective: This study assessed the risk factors for thrombosis related to totally implantable venous access ports (TIVAPs) among breast cancer patients., Methods: A single-center, retrospective, observational study was conducted. Demographic, disease-related, hematological, and TIVAP-related factors were assessed. Multiple logistic regression analysis was used to explore the influencing factors of TIVAP-related thrombosis., Results: A total of 416 patients with breast cancer with TIVAPs were divided into 3 groups: no thrombosis (64.4%), asymptomatic thrombosis (32.3%), and symptomatic thrombosis (3.3%). Multiple logistic regression showed that with no thrombosis as the reference, the protective factors for asymptomatic thrombosis were chemotherapy and TIVAP placement in the left side of the chest wall. Risk factors were ≤1 comorbidity and the use of ceramics as the base material of the TIVAP reservoir. With no thrombosis as the reference, cancer clinical stage III and chemotherapy were identified as protective factors of symptomatic thrombosis., Conclusion: Among breast cancer patients with a TIVAP, 32.3% had asymptomatic thrombosis and 3.3% had symptomatic thrombosis. Clinical staff should pay close attention to these indicators and identify high-risk patients with TIVAP-related thrombosis as early as possible., Competing Interests: Conflicts of Interest: The authors report no conflicts of interest., (Copyright © 2025 Infusion Nurses Society.)