Morin is a flavone extracted from the family Moraceae (Morus Alba L.) having various pharmaceutical activities such as, anti-oxidation, anti-inflammation and anti–cancer. Here, we investigated anti-carcinogenic effect of morin on human breast cancer cells. The result showed that morin regressed metastatic potential in MCF-7 (ER-positive), MDA-MB-231 (triple-negative) and SK-BR-3 (HER2 overexpression) cells through the inhibition of cell migration and matrix metalloproteinase-9. Furthermore, ER and HER2 expressions were decreased by morin in MCF-7 and SK-BR-3 cell, respectively. In addition, we found cytotoxic activity of morin in MDA-MB-231 thorough the increases of P21 expression and H2A.X phosphorylation regulated by ERK 1/2 signaling pathway. We also revealed that anti-metastatic potential in MCF-7 was linked with the suppression of c-Jun and c-Fos expression mediated by down-regulation of GSK3β phosphorylation. In conclusion, this investigation suggests that morin is an effective candidate for breast cancers treatment characterized as ER-positive, triple-negative and HER2 overexpression. [This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2018R1D1A1B07047758)]