Purpose: Limited risk assessment tool to stratify the risk of PICC-related thrombosis (PICC-RVT) in breast cancer patients. This study developed a model to assess the risk of PICC-RVT in breast cancer patients. Methods: We conducted a retrospective cohort study of 1284 breast cancer patients receiving PICC insertion during 1 January 2015 - 31 August 2019 at a cancer specialized hospital in Hunan province, China. The entire population is divided into two groups at a ratio of 3:1 which included a derivation sample (n=978), and a validation sample (n=284). PICC-RVT was confirmed by ultrasonography in the presence of clinical symptoms and signs. Results: PICC-RVT occurred in 40 (4.09%) of the derivation sample patients. Multivariable analysis identified 9 variables: chronic obstructive pulmonary disease, prior central venous catheter placement, higher level of Platelets, higher level of D-dimer, lower level of Activated partial thromboplastin time, menopause, no prior breast surgery, upper extremity lymphedema, and endocrine therapy. Points were assigned to each variable according to regression coefficient. The model had an area under the receiver operating characteristics curve (AUC) of 0.850 (95% CI 0.776 to 0.924), The Hosmer-Lemeshow goodness of fit was 4.781 (p=0.572). At a cutoff value of 3.5, the sensitivity and specifcity were 75% and 83%, respectively.Conclusion: Several disease-specific factors of breast cancer (e.g., menopause, endocrine therapy and upper extremity lymphedema) play important roles in the development of PICC-RVT. Patients at higher PICC-RVT risk could be candidates for close post-insertion monitoring and interventions to prevent PICC-RVT.