Breast cancer is one of the most important global health problems affecting both developed and developing countries. The identification of anticancer compounds, effective on breast cancer cells, is of key importance in chemoprevention investigations and drug development studies. In the literature, there are numerous compounds that have been analyzed for their cytotoxic effects on breast cancer cells, but there is no database where the researchers who want to design a new study on breast cancer can find these compounds all at once. This paper presents a relational database that stores the data of natural and synthetic compounds cytotoxically active on breast cancer cells. The database contains 381 cytotoxicity results and data of 159 compounds, compiled from selected 80 studies. When all this data in our database was queried, it was found out that quercetin, which is a dietary flavonoid, is the most analyzed compound, and MCF-7 cell line is the most used breast cancer cell line.