This study investigates the effectiveness of tuned mass damper (TMD) systems in mitigating torsional irregularities impact on seismic response of L-shaped reinforced concrete (RC) buildings, with a particular emphasis on soil–structure interaction (SSI) effects. Nonlinear time history analyses were conducted on a nine-story RC building constructed on both ZC (moderate) and ZD (soft) soil types, under three different conditions: fixed-base, SSI without control, and SSI with TMD control. The SSI effects were modeled using a substructure approach, and 15 bidirectional ground motion records were used for input excitation for each case. This paper presents a novel configuration of TMDs on building roof; the effectiveness of TMD in mitigating seismic responses of L-Shaped RC Structures subjected to a range of earthquake ground motions is assessed. This study investigates how torsional behavior is affected by soil–structure interaction (SSI) and how this behavior can be mitigated through the implementation of TMDs. The outcome results show that SSI notably amplifies torsional responses, especially in soft soils, leading to higher exceedance probabilities of the torsional irregularity index η_bi. The introduction of the TMD control system significantly reduced torsional irregularities impact on seismic demands, with a reduction exceeding 12 % in upper stories for ZD soils. Fragility curves further confirmed the TMD’s effectiveness in reducing the probability of torsional irregularity impact exceedance. These findings highlight the necessity of incorporating SSI effects on seismic demands assessment and the effectiveness of TMD control devices for seismic mitigation as a seismic design approach for irregular RC buildings.