Objective: To assess the expression of ARHGEF19 in human breast cancer, investigate its role in breast cancer, and clarify the mechanism. Methods: Bioinformatics analysis, immunoblot, quantitative PCR, and immunohistochemical (IHC) assays were performed to assess ARHGEF19 expression in breast cancer. CCK-8 and Edu assays were conducted to reveal its role in breast cancer cell proliferation. Flow cytometry (FCM) assays and immunoblot were performed to confirm its effects on breast cancer apoptosis. Immunoblot was also performed to clarify the mechanism. Finally, tumor growth assays were aimed to confirm the role of ARHGEF19 in mice. Results: We observed that ARHGEF19 was highly expressed in human breast cancer. ARHGEF19 promoted breast cancer cell growth in vitro, and suppressed apoptosis. In addition, we found that ARHGEF19 could activate the MAPK pathway in breast cancer cells. Our findings further confirmed that ARHGEF19 contributed to breast cancer growth in mice. Conclusion: We observed that ARHGEF19 promoted the growth of breast cancer in vitro and in vivo via MAPK pathway, and presume it could serve as a breast cancer therapeutic target.  Kulcsszavak: ARHGEF19, proliferation, apoptosis, MAPK pathway, therapeutic target