Two new and two known compounds were identified as estrogenic constituents from Broussonetia kazinoki. Their structures were elucidated as broussonin A (1), tupichinol C (2), kazinol U (3), and (+)-(2R) kazinol I (4). They showed estrogenic activity with ligand-binding activity of estrogen receptor, transcriptional activity of estrogen-responsive element-luciferase reporter genes. They also control the cellular gene expression levels of estrogen-responsive genes. Phytoestrogens from B. kazinoki may have beneficial effects in the treatment of menopausal symptoms.