Objective To explore the clinicopathological features of bilateral primary breast cancer (BPBC) at different ages. Methods Clinical data of 105 BPBC patients admitted to the Department of Breast Surgery in The First Affiliated Hospital of Zhengzhou University from January 2017 to January 2020 were collected and divided into young group (≤40 years old) and middle-old group (>40 years old) according to age. The characteristics and differences of bilateral tumor lesions in pathological type, molecular type, tumor diameter, histological grade, clinical stage, lymph node metastasis, recurrence or distant metastasis, immunohistochemical indexes expression characteristics, consistency and difference, and overall prognosis between the two groups were retrospectively analyzed. Results There were statistically significant differences between the two groups in the size of the first primary cancer, lymph node metastasis, the high expression rate of Ki-67 in the second primary cancer, clinical stage of double primary cancer and recurrence or distant metastasis (P<0.05). In the young group, the proportion of the first primary cancer with T3–T4 stage was higher, the incidence of lymph node metastasis was higher, the proportion of high expression of Ki-67 in the second primary cancer was higher, and the proportion of patients with double primary cancer at first diagnosed as stage Ⅳ were higher than those in the middle-old group, and were prone to recurrence or distant metastasis. The expression of immunohistochemical indexes in bilateral cancer foci was consistent between the two groups (P<0.05). The expression consistency of ER and Ki-67 in the young group was better, and the expression consistency of PR and HER-2 in the middle-old group was better. The histological grade of the first primary cancer, TNM stage of bilateral primary cancer and recurrence or metastasis were independent factors affecting the prognosis of patients (P<0.05). Conclusions The BPBC patients of different ages have different clinicopathological features, and the expression of immunohistochemical indexes in bilateral cancer foci is consistent. Tumor histological grade of the first primary cancer may affect the prognosis of patients with BPBC, and the prognosis of patients with early bilateral TNM stage is better.