Objective: This study aimed to correlate the immunohistochemical expression of fatty acid synthase (FASN) and HER-2 with the clinicopathological variables in breast infiltrating duct carcinoma (IDC) to identify the impact of marker expression on tumor behavior and mammary carcinogenesis and to detect the correlations between the two markers. Methods: Immunohistochemical expressions of FASN and HER-2 were evaluated in 77 breast case including 10 normal breast, 12 ductal carcinoma in situ (DCIS) and 55 IDC and correlated with clinicopathological variables. The obtained data were statistically analyzed. Results: FASN was overexpressed in 91.7% and 70.9% of DCIS and IDC, respectively, with a significant difference from the normal (P= 0.000). In IDC, the expression of FASN was significantly more expressed in low-grade IDC (P= 0.031). FASN was significantly upregulated in larger tumors and lymph node metastasis (P= 0.017 and P= 0.046, respectively). The expression of FASN had a significant negative correlation with progesterone receptor (PR) (P= 0.05).HER-2 was overexpressed in 50% and 25.45% of DCIS and IDC, respectively, with a significant difference from the normal (P= 0.026). HER-2 was only expressed in high-grade DCIS (P= 0.007). In IDC, the expression of HER-2 was significantly up-regulated in larger tumors and lymph node metastasis (P= 0.033 and P= 0.015, Respectively). The expression of HER-2 had a significant negative correlation with estrogen receptor (ER) and PR (P= 0.001 and P= 0.023, respectively). Correlation between the expression of FASN and HER-2 in IDC, revealed a significant positive correlation (Spearman correlation [r] = 0.374, P= 0.005). Conclusions: We concluded that over expression of FASN and HER-2 may facilitate the early diagnosis of IDC. In IDC, their over expression might warn of a more aggressive course. Our correlation found that FAS expression is closely associated with over expression of HER-2 in IDC.