Western boundary currents (WBCs) play an essential role in regulating global climate. In contrast to their widely examined horizontal motions, less attention has been paid to vertical motions associated with WBCs. Here, we examine the vertical motions associated with the major WBCs by analyzing vertical velocity estimates from five ocean synthesis products and one eddy-resolving ocean simulation. These data reveal robust and intense subsurface upwelling in five major subtropical WBC systems. These upwelling systems are parts of basin-scale zonal overturning circulations and are likely driven by the meridional pressure gradients along the western boundary. The intense subsurface upwelling associated with WBCs and the basin-wide zonal overturning circulations are potentially crucial for the transport of properties and materials in the ocean interior but have long been neglected in the literature. This study suggests an overlooked role of WBCs in the climate system and showcases the usefulness of ocean vertical velocity estimates from various data products.