Theuse of hormone therapy has side effects in the breast which detected on ultrasound by increasing the thickness of breast fibroglandular tissue associated with increased risk of breast. Until now there is still controversy regarding the side effects of tibolon on the breast tissue. This study aims to determine the thickness changes of the fibroglandular tissue due to tibolon hormone therapy. This research was done between December 2013 untill August 2015 in Department of Radiology, dr. Cipto Mangunkusumo Hospital. Design of this research is a quasi-experimental study with the amendment in the form of data retrieval breast ultrasound before and after tibolon hormone therapy. Measurements with breast ultrasound was done in four regions (superior, inferior, medial and lateral) then the average change in fibroglandular thickness was analyzed. Of the 40 subjects were analyzed, there were 36 subjects showed significant increase (p <0.001) of breast fibroglandular tissue thickness after 3 months of tibolon hormone therapy. The body mass index (p = 0.02) and a history of hormonal contraception (p = 0,01) were factors that influence the increase of fibroglandular thickness post tibolon hormone therapy. While parity, age of first child, history of breastfeeding, age of menarche, age of menopause and history of hormonal contraception were not related.