Signal transducers and activators of transcription 3 (STAT 3) have been proposed to be responsible for breast cancer development. Moreover, evidence depicted that upregulation of STAT3 is responsible for angiogenesis, metastasis, and chemo-resistance of breast cancer. Tamoxifen (TAM) resistance is a major concern in breast cancer management which is mediated by numerous signaling pathways such as STAT3. Therefore, STAT3 targeting inhibitors would be beneficial in breast cancer treatment. The information on the topic in this review was gathered from scientific databases such as PubMed, Scopus, Google Scholar, and ScienceDirect. The present review highlights STAT3 signaling axis discoveries and TAM targeting STAT3 in breast cancer. Based on the results of this study, we found that following prolonged TAM treatment, STAT3 showed overexpression and resulted in drug resistance. Moreover, it was concluded that STAT3 plays an important role in breast cancer stem cells, which correlated with TAM resistance.