It has been suggested that transient receptor potential melastatin 4 (TRPM4) cation channels are abundantly expressed in the prostate gland. However, the precise role of TRPM4 channels in prostatic smooth muscle contractility is still unknown. Here, we examined if TRPM4 channels are involved in the adrenergic contraction in mouse prostatic smooth muscles. Adrenergic contractile responses evoked by electrical field stimulation of intrinsic sympathetic nerve or exogenously applied noradrenaline (NA) were isometrically recorded and effects of 9-phenanthrol, a specific and potent TRPM4 channel inhibitor, on those contractile responses were investigated in mouse ventral prostate preparations. 9-phenanthrol (10 and 30 μM) concentration-dependently inhibited both sympathetic nerve-evoked contractions and NA-induced contractions. The percentage inhibition by 9-phenanthrol was much greater at lower stimulus frequencies and lower NA concentrations. However, the agent did not inhibit NA-induced contractile response due to release of stored Ca²⁺. These results suggest that TRPM4 channels are involved in the adrenergic contraction possibly through membrane depolarization by their opening and seems to be a potential candidate for the treatment of benign prostatic hyperplasia.