Poly(ADP-ribose) polymerase-1 (PARP-1) is a new potential target for anticancer drug discovery. A series of bromophenol-thiosemicarbazone hybrids as PARP-1 inhibitors were designed, synthesized, and evaluated for their antitumor activities. Among them, the most promising compound, 11, showed excellent selective PARP-1 inhibitory activity (IC50 = 29.5 nM) over PARP-2 (IC50 > 1000 nM) and potent anticancer activities toward the SK-OV-3, Bel-7402 and HepG2 cancer cell lines (IC50 = 2.39, 5.45, and 4.60 μM), along with inhibition of tumor growth in an in vivo SK-OV-3 cell xenograft model. Further study demonstrated that compound 11 played an antitumor role through multiple anticancer mechanisms, including the induction of apoptosis and cell cycle arrest, cellular accumulation of DNA double-strand breaks, DNA repair alterations, inhibition of H2O2-triggered PARylation, antiproliferative effects via the production of cytotoxic reactive oxygen species, and autophagy. In addition, compound 11 displayed good pharmacokinetic characteristics and favorable safety. These observations demonstrate that compound 11 may serve as a lead compound for the discovery of new anticancer drugs.