This study aimed to assess the impact of estrogen receptor grade of positivity on the outcome of estrogen receptor positive breast cancer patients receiving adjuvant tamoxifen. This retrospective study included 100 ER-positive breast cancer patients who received adjuvant tamoxifen and followed up in the period from June 2009 until December 2018. Levels of ER staining intensity was measured as the percentage of cells staining positive for ER by immunohistochemistry and graded as mild (1-10%), moderate (11-50%) and high (> 50%). The degree of intensity was correlated disease free survival (DFS) and overall survival (OS).. Only one patient had weak ER positivity, 49% was moderate while 50% of cases had strong positivity. Patients with strong ER positive disease had significantly prolonged OS (p=0.018) and superior DFS but of borderline significance (p=0.064) when compared with moderate or weak positivity. There is growing body of evidence supporting the utility of degree of estrogen positivity as prognostic factors hormone receptor positive breast cancer patients.