Poly(ADP-ribose) polymerase (PARP) inhibitors have been approved and marketed for the treatment of BRCA-mutated breast and ovarian cancers. Recent studies have demonstrated that cyclin-dependent kinase 4/6 (CDK4/6) inhibitors can induce defects in homologous recombination (HR) repair, thereby sensitizing breast cancer cells with HR proficiency to PARP inhibitors through a synthetic lethal mechanism. Here, we report the rational design and synthesis of a potent dual PARP/CDK6 inhibitor 11, which was identified through SAR studies. Compound 11 effectively induces excessive DNA damage and apoptosis in MDA-MB-231 cells, while maintaining robust inhibitory activity against both PARP and CDK6. Additionally, 11 demonstrates excellent antitumor efficacy and antimetastatic properties, with no evident toxicity or side effects observed. Further investigations revealed that 11 could inhibit tumor cell proliferation by modulating the Wnt/β-catenin signaling pathway. In summary, these findings highlight the potential therapeutic advantages of 11, coded with KWZY-11, in treating BRCA wild-type tumors.