Although remarkable studies are reported about active structural control of seismically excited building structures and different control algorithms are introduced, most of the available control strategies have neglected the effects of time-delay in the control system. However, the time-delay has a significant influence on the control performance so that instability in responses may occur if time-delay is not considered in design of controllers and their control algorithms. In this paper, two types of controllers (state feedback and dynamic output feedback controllers) are designed for vibration suppression of seismically excited building structures considering the effects of time-delay. To this aim, the dynamic differential equations of a system with an artificial time-delay are first written. Then, the dynamic system is converted into delay-free equations by using a special integral transformation. Finally, state feedback and dynamic output feedback controllers are designed by using the [Formula: see text] control theory. Simulation results show that the suggested control algorithms can effectively suppress the vibrations of building structures under time-delay conditions.