Dynamic Substructuring & Transfer Path Analysis, Volume 4: Proceedings of the 43rd IMAC, A Conference and Exposition on Structural Dynamics, 2025, the fourth volume of twelve from the Conference brings together contributions to this important area of research and engineering. The collection presents early findings and case studies on fundamental and applied aspects of the dynamics of coupled structures, including papers on:Linear Joints, Nonlinear Joints and CouplingModal and Frequency Based SubstructuringRound Robin Test Bed on Dynamic SubstructuringTransfer Path Analysis and Force EstimationInterface Dynamics