The effect of the lift augmentation of multi-element airfoils with increased flap deflection and dielectric barrier discharge (DBD) plasma flow control on the flap at several angles of attack (AOAs) is investigated numerically and experimentally. A phenomenological body force model is employed to simulate the DBD actuators at Re = 1.03 × 106. The simulation results show that the atmospheric plasma generated by the DBD actuators completely suppresses the flow separation over the flap at several AOAs, and consequently, the lift augmentation of a multi-element airfoil can be achieved over the entire prestall AOA range. A corresponding flow control experiment on a multi-element airfoil performed in a low-speed wind tunnel at a freestream velocity of 30 m/s is presented; in this experiment, particle image velocimetry (PIV) was employed for flow visualization over the upper surface of the flap. The PIV results demonstrate that the flow separation on the flap is suppressed completely by the same DBD actuators used in the simulation.