Objective To evaluate the diagnostic value of T1 Mapping combined with diffusion-weighted imaging (DWI) in differentiating benign and malignant breast masses, and to analyze its correlation with Ki-67 expression. Methods A total of 96 patients with pathologically confirmed breast masses were retrospectively enrolled. The differences in T1 value, post-contrast T1 (T1+) value, percentage change of T1 (△T1%), T2 value and apparent diffusion coefficient (ADC) were compared between benign and malignant masses. Logistic regression analysis was used to construct a combined diagnostic model, followed by receiver operating characteristic (ROC) curve analysis. Meanwhile, the Spearman correlation between MRI quantitative parameters and Ki-67 expression was evaluated. Results The T1 value, T1+ value and △T1% of malignant masses were significantly higher than those of benign masses, while the ADC was significantly lower (all P＜0.05). Multivariate analysis showed that △T1% and ADC were independent predictors for malignant breast masses. The area under the curve (AUC) of the combined model was 0.941, which was superior to all individual MRI quantitative parameters. In the high Ki-67 expression group, △T1% was increased and ADC was decreased (both P＜ 0.05). Moreover, △T1% was positively correlated with Ki-67 (r＝0.462), and ADC was negatively correlated with Ki-67 (r＝?0.518). Conclusion T1 Mapping combined with DWI can significantly improve the diagnostic efficiency in differentiating benign and malignant breast masses. △T1% and ADC have important diagnostic value and can reflect the proliferative activity of breast tumors.