ProTargetMiner is the first publicly available expandable proteome signature library of anticancer molecules in cancer cell lines. Based on 287 A549 adenocarcinoma proteomes affected by 56 compounds, the main dataset contains data on 7,328 proteins and 1,307,859 refined protein-drug pairs. The proteomic signatures cluster into groups by the compound targets and action mechanisms. The targets and mechanistic proteins can be deconvoluted by partial least square modeling provided online through an R Shiny package and a website (http://protargetminer.genexplain.com). For 9 molecules representing most diverse action mechanisms and common cancer cell lines MCF-7, RKO and A549, deep proteome datasets were obtained. Combining the data from the three cell lines identified common drug targets and mechanisms, while also highlighting important cell-specific differences. ProTargetMiner can also provide information on resistance factors, affected protein complexes and drug metabolizing enzymes. The database can be easily extended and merged with new compound signatures. We expect ProTargetMiner to serve as a valuable chemical proteomics resource for the cancer research community, and become a popular tool in drug discovery.