Although the relationship between breast cancer (BC) risk factors and mammographic density (MD) patterns is not clear, high MD is well known as an independent risk factor for BC. Thus, the aim of this study was to examine the association between MD and BC risk factors in BC patients and find a correlation between MD and tumor characteristics in BC patients. Our data included 242 patients with BC. Furthermore, the MD (type I - <25%; type II - 25-50%; type III - 51-75%; and type IV - >75%) was categorized according to percentile density, and the various types of MD were compared using risk factors for BC and tumor characteristics of patients. The results of this study indicated that younger age, pre-menopausal status, younger menarche age, nulliparity, low body mass index, and smoking significantly increase the percentage of MD (p<0.001, p<0.001, p=0.04, p<0.001, p=0.003, and p=0.01, respectively). Moreover, the distribution of MD patterns showed significant differences according to tumor subtypes. Type 4 mammographic pattern was higher in patients with human epidermal growth factor receptor 2 (Her2) type of tumor (p=0.01). Higher MD is related to reproductive risk factors and tumor subtypes, especially Her2 type, in BC patients. Further studies are needed to identify the factors related to breast density.