A three-dimensional liquid metal magnetohydrodynamic (LMMHD) flow in a manifold with three subchannels under a uniform magnetic field has been examined based on the computational fluid dynamics method. Although numerous analytic, experimental, and numerical studies on LMMHD duct flows have been performed, detailed flow characteristics of a LMMHD flow in a manifold with multiple channels have not been studied much. In the current study detailed behaviors of the fluid velocity, pressure, current, and electric potential of LMMHD flows in a manifold with three subchannels under a uniform magnetic field are elucidated. Also, an imbalance of mass flow rates in the three subchannels is addressed.