In this study, a tuned liquid mass damper (TLMD) was proposed to reduce bidirectional responses of building structures, and its control performance was experimentally evaluated. The proposed TLMD with only one device body reduces bidirectional responses of building structures by behaving as a TMD and a TLCD in the weak and strong axial directions of a building fl oor plan, respectively. First, the control performance of a TLMD mounted on a scaledowned single-degree-of-freedom building model was experimentally evaluated by exciting this system with an actuator. Then, the real-time hybrid shaking table testing method (RTHSTTM) was performed to assess the control effi ciency of the total system by adopting the TLCD and the building model as the experimental and numerical parts, respectively. It was confi rmed by comparing uncontrolled and controlled testing results that the proposed TLMD can be applied to reduce the responses in both the weak and strong directions of building structures. Also, the results from RTHSTTM showed that the performance of TLMD-controlled building structure can be accurately evaluated by this method only using a TLMD as the experimental part.