Abstract With the recent popularity of the tide‐resolving and submesoscale‐admitting numerical simulations, there is an increasing interest in separating vortical and wavy motions in the ocean. The recently‐proposed dynamics‐based decomposition exploits the relative magnitude of the relative vorticity and horizontal divergence in Fourier space and proves efficient. In this decomposition, physical variables over non‐water regions (e.g., coasts, islands, seamounts) are filled with zeros following standard practice. This zero‐filling would adversely affect the accuracy of vortical‐wavy separation, however. To mitigate this effect, this study adopts a streamline‐following perspective. With physical variables projected along the streamline and dynamics‐based decomposition adjusted accordingly, we get a boundary‐aware separation of vortical and wavy motions. The potential usefulness of this approach is demonstrated through its application to data from a high‐resolution numerical simulation.