<p>Air compressor systems for fuel-cell vehicles typically require downsizing, high-performance, and cost reduction. With increasing air compressor performance requirements, attention must be paid to the cooling methods that combine a coolant and air cooling. To reduce the number of system packages and parts, a study was conducted on internal self-air cooling by applying a hollow shaft to an air compressor using an airfoil bearing. The results indicated that although the aerodynamic performance was degraded owing to impeller leakage and recirculating flow, the axial force was reduced; thus, the overall compressor efficiency was not reduced significantly. Several advantages were confirmed numerically and experimentally. The obtained configuration does not require an air-cooling supply unit for the motor and bearing, which simplifies the product configuration. This system can also reduce the thrust bearing size by reducing the axial force. Furthermore, the recirculating flow through the hollow shaft can increase the surge margin, which is an indicator of the operating range of the compressor.</p>