Because of the abnormal upregulation of matrix metalloproteinase (MMP) activities in tumors, MMP inhibitors (MMPIs) are validated anticancer drug candidates. We identified several MMPIs including mangiferin as an MMP-9 inhibitor with a half maximal inhibitory concentration (IC50) value of 250 nM, isosilybin as an MMP-13 inhibitor with an IC50 value of 250 nM, and isoliquiritigenin as a broad-spectrum MMPI (with IC50 values of 16 nM for MMP-1, 10 nM for MMP-2, 81 nM for MMP-3, 8 nM for MMP-7, 10 nM for MMP-9, and 14 nM for MMP-13) through studying the interactions of 6 MMPs secreted by U-2OS cells with 51 phenolic natural products on the peptide microarray platform. In addition, the inhibitory mechanisms of as-discovered MMPIs were evaluated by a molecular docking simulation. The antitumor efficiencies of MMPIs were demonstrated by both a cell scratch test and growth suppression of mouse-born OS tumors. The results of the cell scratch test suggested that isoliquiritigenin significantly inhibited the migration of U-2OS cells. In addition, administration of isoliquiritigenin significantly reduced the tumor size (by about 80%) and prolonged the survival time (by more than 70 days). This study suggests that the discovery of MMPIs from phenolic natural products is a meaningful way to screen anticancer agents.