This study experimentally evaluates the seismic performance of knee braced moment resisting frame (KBRF) systems. A series of cyclic load tests were performed on the special moment resisting frame (SMRF) and KBRF systems with in-plane and out-of-plane controlled buckling mechanisms in the knee braces. It was found from the test results that the strength and energy dissipation capacity of the KBRFs was significantly enhanced regardless of whether the knee braces buckled in the in-place or out-of-plane direction. Further test result comparisons demonstrated that the allowable drift at which the knee braces reached the buckling stage was higher for KBRF frames equipped with in-plane buckling braces. It is therefore suggested that braces with in-plane buckling modes be adopted for greater earthquake resistance in KBRF frame structure designs.