<p>Non-circular piles exhibit remarkable superiority in lateral bearing capacity and seismic performance due to their geometric advantages. However, the complex boundary effects induced by their asymmetric cross sections pose significant theoretical challenges to the analytical characterization of dynamic soil–pile interaction mechanisms at the interface. To address these challenges, an analytical–numerical coupling calculation framework for non-circular pile dynamics is established, where the fundamental dynamic equation of the coupled pile-viscoelastic soil system is derived through variational formulations and Hamilton's principle. The proposed method effectively reduces the three-dimensional (3D) pile–soil interaction problem under dynamic loading to a coupled solution between soil dynamics equations in two-dimensional (2D) space and one-dimensional (1D) pile governing equations. An adaptive numerical iteration algorithm is subsequently employed to solve the governing equations, significantly improving computational efficiency for lateral dynamic pile–soil interaction problems. The proposed approach demonstrates its reliability when evaluated against finite element simulations and existing analytical solutions. A detailed analysis is performed to examine how soil layer properties, the cross-sectional geometry of non-circular piles, and slenderness ratios influence the lateral dynamic response behavior.</p>