Aim: To investigate whether tumor-infiltrating lymphocyte (TIL) scoring based on 18F-fluorodeoxyglucose positron-emission tomography/computed tomography (FDG PET/CT) can predict the pathological response to neoadjuvant chemotherapy. Patients and Methods: A total of 261 patients with breast cancer underwent complete resection after neoadjuvant chemotherapy. PET-TIL score was calculated using tumor size, Ki-67 labeling index, and maximum standardized uptake value (SUVmax) on FDG PET/CT. The efficacy of the PET-TIL score in predicting the pathological complete response (pCR) was retrospectively evaluated. Results: pCR rates were 11.4%, 58.6%, and 38.8% in luminal, human epidermal growth factor receptor 2 (HER2)-positive, and triple-negative breast cancer, respectively. The corresponding median PET-TIL scores were 28, 37, and 45. pCR rates were 20.0% and 44.2% in the low and high PET-TIL score groups, respectively (p<0.001). HER2-positive and triple-negative subtypes and high PET-TIL score were independent predictors for pCR. Conclusion: PET-TIL score can predict pCR after neoadjuvant chemotherapy in breast cancer.