OBJECTIVE: To explore the correlation between breast MRI findings, quantitative parameters, and tumor-infiltrating lymphocyte (TIL) level of patients who emphasized radiotherapy after with triple-negative breast cancer (TNBC). STUDY DESIGN: Forty-five TNBC patients underwent 3.0 T breast MRI examination, and the diagnosis of patients were confirmed by core needle biopsy. The apparent diffusion coefficient (ADC) histogram was generated using Firevoxel software, and multiple ADC histogram parameters were recorded, including ADCmin, ADCmean, ADCmax, skewness coefficient, and kurtosis coefficient. The proportion of TILs in the puncture specimens was calculated. All patients were followed for 3 years, and the local regional recurrence rate (LRR) was observed. The propensity score matching method was used to analyze the difference in MRI quantitative parameters and the proportion of TILs in patients with and without recurrence during the follow-up period. Pearson correlation was used to analyze the correlation between MRI quantitative parameters and the proportion of TILs. The receiver operating curve (ROC) was used to analyze the value of MRI quantitative parameters and proportion of TILs to predict the recurrence in patients who emphasized radiation therapy after TNBC. RESULTS: The 3-year LRRs of the 45 patients after postoperative follow-up were 6.82% (3/44) in the first year, 12.2% (5/41) in the second year, and 23.08% (9/39) in the last year. During the follow-up period the differences in MRI quantitative parameters and TIL ratios of patients with local regional recurrence were statistically significant. Spearman correlation analysis indicated that MRI quantitative index and proportion of TILs were significantly correlated. ROC analysis suggested that MRI quantitative parameters and proportion of TILs had predictive value for local regional recurrence. CONCLUSION: The quantitative parameters of preoperative MRI and the proportion of TILs in patients who emphasized radiotherapy after TNBC were significantly correlated. Preoperative MRI quantitative parameters and the proportion of TILs had predictive value for local recurrence in patients who emphasized radiation therapy after TNBC. © Science Printers and Publishers, Inc.