Seismic structure related to the magmatic system beneath the potentially hazardous Changbaishan volcano recently becomes hotly debated. In addition, mantle flow dynamics throughout the back‐arc regions in NE Asia remain poorly constrained due to the lack of seismic data in the Korean Peninsula and surrounding ocean regions. In this study we construct a high‐resolution azimuthally anisotropic Rayleigh‐wave phase velocity model in NE Asia, by integrating seismic data from China, North Korea, South Korea, and Japan. The resulting isotropic velocity maps suggest possible existence of a crustal magma chamber beneath the Changbaishan volcano and that the widespread intraplate volcanism in NE Asia likely arises from the upwelling asthenosphere. The obtained anisotropic maps reveal trench‐normal return flow patterns in the back‐arc regions of NE Asia with local variations between East China and northeast China as controlled by the subduction geometry of the Pacific slab. Plain Language Summary The transition from a more subduction‐driven geodynamic setting to a continental one in NE Asia makes it an ideal laboratory for investigating the formation and evolution of continental intraplate volcanism associated with mantle dynamics. However, due to the lack of seismic data in the Korean Peninsula and surrounding ocean regions, seismic structures beneath these intraplate volcanoes and mantle flow dynamics operating in this region are still not well resolved. We build a high‐resolution seismic velocity model of NE Asia in this study by utilizing seismic data collected from China, North Korea, South Korea, and Japan. We find significant low‐velocity anomalies in the middle‐lower crust beneath the Changbaishan volcano, which indicates there might be a deep crustal magma chamber beneath this giant volcano. In the upper mantle region, the intraplate volcanoes are underlain by markable low seismic velocities, suggesting that the intraplate volcanism is likely to originate from the upwelling asthenosphere. Our seismic imaging results in East and NE China confirm previous studying results that claim the subduction geometry of the Pacific slab results in different mantle flow patterns in East and NE China. The subducting Pacific slab is also responsible for the trench‐normal fast direction observed within the back‐arc regions. Our presented model provides seismic constraints and deepens our understanding on the intraplate volcanism and associated mantle dynamics in NE Asia. Key Points A middle‐lower crustal magma chamber is imaged beneath the Changbaishan volcano Intraplate volcanism in NE Asia is likely fed by upwelling asthenosphere Trench‐normal return flow patterns with local variations between East and northeast China are revealed in the back‐arc regions of NE Asia