Objectives: This study investigates the relationship between 18fluoride-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) parameters and histopathological features in patients with early-stage invasive ductal breast carcinoma (IDBC). Methods: Patients with early-stage IDBC who underwent 18F-FDG PET/CT scan for staging were included in this retrospective study. The status of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2, Ki-67 proliferative index, and grades of tumors were recorded. The conventional metabolic parameters [maximum standard uptake value (SUVmax) and average standard uptake value] and volume-based parameters [metabolic tumor volume (MTV) and total lesion glycolysis] of the primary tumor were obtained from the 18F-FDG PET/CT images. The associations and correlations between the 18F-FDG PET/CT parameters and histopathological features were assessed. Results: One hundred forty-three patients were included. 18F-FDG PET/CT parameters, other than MTV, were significantly associated with the ER and PR status and Ki-67 index, while T-staging was significantly associated with all 18F-FDG PET/CT parameters. In the axillary lymph node (ALN) involvement, no significant difference was found in the 18F-FDG PET/CT parameters. In terms of the pathological stage, a significant difference was found in all 18F-FDG PET/CT parameters. 18F-FDG PET/CT parameters, other than MTV, were significantly higher in non-luminal breast tumors than luminal tumors and in high-grade tumors than low-grade ones. Triple-negative tumors had the highest 18F-FDG PET/CT parameter, but the difference was insignificant for MTV. The SUVmax had the strongest correlation with Ki-67 proliferative index. Conclusion: Tumors with aggressive histopathological features had higher 18F-FDG PET/CT parameter values. This study suggests that 18F-FDG PET/CT may provide prognostic information in patients with early-stage IDBC.