Traditional methods for assessing the seismic behavior of high-rise buildings often involve complex and computationally intensive models that explicitly account for the detailed behavior of the coupled system and their interactions. While accurate, these methods can be prohibitively time-consuming and resource-intensive, especially for preliminary design or assessment purposes. The concept of equivalent pile approach has been used in this study to overcome these issues. This method simplifies the complex SPSI problem by representing the entire pile group with an equivalent single pile that possesses similar dynamic characteristics. The pile characteristics such as slenderness ratio (L/D), spacing (S/D), and end-fixity of the piles significantly influence the seismic performance of high-rise buildings. The present study aims to investigate the influence of slenderness ratio, and spacing between the piles on the seismic performance of high-rise building through an equivalent pile approach. This study utilizes a three-dimensional finite element model of 20-storey, and pile foundations with varying slenderness ratios and spacing. The significance of SPSI has been estimated by comparing the responses of the system for fixed-base and flexible-base conditions. The seismic response of the coupled system has been estimated and is expressed in terms of fundamental time period. The seismic performance of the foundation has also been estimated and expressed in terms of rocking. It is found that the estimation in the fundamental period obtained by the equivalent pile approach only shows a non-significant variation ranging between 3.11% to 4.69% from the experimental results, and also reduces the computation time by 12–16 h. These observations show that the equivalent pile approach is an efficient approach for soil-pile-structure interaction studies. It is also found that the fundamental period reduces in the range of 3.65%–7.52%, and 6.94%–9.05%, when the slenderness ratio (L/D) of the pile increases from 30 to 80, and spacing (S/D) between the pile increases from 3 to 6, respectively.