Androgen receptor (AR) has proved to be a vital drug target for treating prostate cancer. Here, we reported the discovery of a novel AR antagonist <b>92</b> targeting the AR ligand-binding pocket, but distinct from the marketed drug enzalutamide (Enz), <b>92</b> demonstrated inhibition on the AR ligand-binding domain (LBD) dimerization, which is a novel mechanism reported for the first time. First, a novel hit (<b>26</b>, IC<sub>50</sub> = 5.57 μM) was identified through virtual screening based on a theoretical AR LBD dimer bound with the Enz model. Then, guided by molecular modeling, <b>92</b> was discovered with 32.7-fold improved AR antagonistic activity (IC<sub>50</sub> = 0.17 μM). Besides showing high bioactivity and safety, <b>92</b> can inhibit AR nuclear translocation. Furthermore, <b>92</b> inhibited the formation of the AR LBD dimer, possibly through attenuating the hydrogen-bonding network between the two monomers. This interesting finding would pave the way for the discovery of a new class of AR antagonists.