This study was conducted to investigate the clinicopathological characteristics and prognosis of breast cancer and lung cancer (BC-LC) and provide a theoretical basis for the diagnosis and treatment of BC-LC in clinical work. A retrospective study was conducted on breast cancer (BC) patients in our center from September 2009 to November 2020. The patients were divided into the BC-LC group and the control group. The control group was matched with both, the age at diagnosis and the time of surgery (± 1 year). The clinicopathological factors, overall survival (OS), and hazard ratios (HRs) were evaluated by SPSS. A total of 19,807 BC patients were identified, among whom 124 (0.6%) had lung cancer (LC). Larger BC tumor was the only independent risk factor (OR = 2.454, p < 0.001) for development of LC in BC patients. We found inferior survival in patients with synchronous versus metachronous BC-LC (p = 0.008). We also identified combined with hypertension (HR = 3.917, p = 0.003) was an independent prognostic factor for inferior OS. Therefore, BC patients with larger tumors need close follow-up. Effective prevention and active treatment of hypertension can improve the OS of BC-LC patients.