AbstractA study is carried out for investigating the effectiveness of active control systems for one‐storey torsionally coupled structures. The governing equations of motion of the system are derived. The control forces are obtained using the classical linear optimal control algorithm. The stochastic seismic response of a torsionally coupled controlled system is investigated under important parametric variations such as: uncoupled lateral time period, system eccentricity and ratio of uncoupled torsional to lateral frequency of the system. In order to investigate the effectiveness of the control device, the response of the system with control device is compared with the corresponding system without control device. Further, the controlled response of the torsionally coupled system is compared with the corresponding response of the uncoupled system. It is shown that the control mechanism is also equally effective in reducing the seismic response of a torsionally coupled system. In addition, it is to be noted that the effectiveness of the active control device is overestimated when it is designed without considering the effects of torsional couplin