An experimental study of a closed-loop multiple-input multiple-output (MIMO) control strategy is presented to mitigate flow separation in a compressor cascade. As a result of the highly loaded stator blades a complex three dimensional flow field develops. Concomitantly, flow separation occurs both at the sidewalls and on the suction side of the blades. In order to suppress separation, methods of active flow control are applied. To detect the flow separation phenomena, adequate surrogate variables can be identified by means of PIV measurements. The effect of pulsed blowing through slit nozzles on the sidewalls and the stator blade is evaluated. A multivariable robust H_∞-approach is shown to control the separation phenomena simultaneously. Based on a dynamic decoupling, a classical inverse-based controller (IBC) is even capable of controlling the dominant vortex structures in a decoupled manner. To demonstrate the robustness of the applied methods experimentally, heavy disturbances are simulated. By rejecting them the proposed control algorithms guarantee stable operating conditions. As a result, the performance of the cascade can be significantly increased by means of active flow control.