The importance of architectural asymmetry is investigated to improve the output voltage of TENGs with polyester/spandex blend three-dimensional (3D) spacer fabrics. Different types of TENGs are fabricated by stacking the 3D spacer fabrics, polydimethylsiloxane (PDMS) films, and electrodes with different stack configurations. The 3D spacer fabric TENGs fabricated with higher architectural asymmetry show higher output voltages than those fabricated with lower architectural asymmetry. In particular, the TENG with the PDMS/fabric/fabric configuration shows the highest peak-to-peak output voltage among all types. An increase in the TENG output voltage is attributed to the relatively high architectural asymmetry in the device configuration and the relatively high effective density of triboelectric charge.