A numerical optimization study is used to design a duct for a model of vertical axis hydro-current turbine. The effects of this duct on the power output and torque fluctuations of the turbine model are then examined numerically and experimentally. Relatively good agreement was obtained between the experimental results and numerical predictions especially at higher tip speed ratios. Experimental results show an 85% increase in the maximum power output when the turbine is placed inside the duct. The numerical and experimental torque curves for the turbine also show substantial reductions in the torque fluctuations as a result of ducting.