Under the combined action of environmental and seismic loadings, offshore wind turbines supported by tetrapod piled jacket (TPJ) foundations may experience tilting and rotational failures, and even the shutdown. However, there is still a notable gap in the research on the dynamic response of the TPJ system in this condition, especially in the multilayered clay deposits. This study conducts advanced three-dimensional finite element simulation to investigate the seismic response of TPJ systems in soft-over-stiff clay deposit under the combined influence of wind and wave loadings. The results indicate that with a minor strength ratio between two layers, especially for strength ratios < 0.28, the peak values of the pile bending moment envelopes increases obviously, which is located near the soil layer interface. Near the soil layer interface, a sudden expansion in the soil plastic strain can be observed at this location. When the top layer thickness is substantial, surpassing 0.75 times the pile length, the restraining effect of the bottom stiff layer on the pile results in the peak value of the acceleration response envelopes and a significant reduction in bending moment near the pile end.