, a deciduous tree belonging to Aceraceae, has been used in traditional oriental medicine for treating hepatic disorders, such as hepatitis, cirrhosis, and liver cancer. We evaluated the estrogen-like effects of using an estrogen receptor (ER)-positive breast cancer cell line, namely MCF-7, to identify potential phytoestrogens and found that an aqueous extract of promoted cell proliferation in MCF-7 cells. Five phenolic compounds (-) were separated and identified from the active fraction using bioassay-guided fractionation of crude extract and phytochemical analysis. The chemical structures of the compounds were characterized as vanillic acid (), 4-hydroxy-benzoic acid (), syringic acid (), isoscopoletin (), and ()-ferulic acid () based on the analysis of their nuclear magnetic resonance spectra and liquid chromatography-mass spectrometry data. All five compounds were evaluated using an E-screen assay for their estrogen-like effects on MCF-7 cells. Among the tested compounds, only 4-hydroxy-benzoic acid () promoted the proliferation of MCF-7 cells, which was mitigated by the ER antagonist, ICI 182,780. The mechanism underlying the estrogen-like effect of 4-hydroxy-benzoic acid () was evaluated via western blotting analysis to determine the expression levels of extracellular signal-regulated kinase (ERK), phosphoinositide 3-kinase (PI3K), serine/threonine kinase (AKT), and ERα. Our results demonstrated that 4-hydroxy-benzoic acid () induced the increase in the protein expression levels of p-ERK, p-AKT, p-PI3K, and p-Erα, concentration dependently. Collectively, these experimental results suggest that 4-hydroxy-benzoic acid () is responsible for the estrogen-like effects of and may potentially aid in the control of estrogenic effects during menopause.