Post-tensioned rocking systems are an attractive alternative for timber construction in seismic prone regions. Although experimental results show that these systems can efficiently control structural damage, the high inter-storey drifts and floor accelerations associated with the rocking motion can cause significant non-structural and contents damage, hence reducing the overall performance of the buildings. In this paper, the use of inerters to reduce peak drifts and accelerations and improve the seismic response of post-tensioned rocking CLT buildings is assessed. In a first stage, the performance of bare and protected structures with different levels of apparent mass ratios is evaluated and compared considering a set of 7 records consistent with the displacement design spectrum. Subsequently, a performance-based assessment is conducted considering a database of 202 pulse-like ground motion records. The results of these analyses show that the inerter can effectively reduce inter-storey drifts and floor accelerations demands in rocking timber structures.