This study examines the influence of the El Niño–Southern Oscillation (ENSO) on the ionospheric total electron content (TEC) diurnal eastward 3 (DE3) and stationary planetary wave 4 (SPW4) which are the major components of the ionospheric wave-4 longitudinal structure. The TEC is the integration of electron density from 200 to 800 km sounded by the GPS radio occultation experiment onboard the FORMOSAT-3/COSMIC satellites during the period of January 2007–December 2015. The results show that the TEC DE3 and SPW4 amplitudes respond to the ENSO signature in the thermospheric wind DE3 in the Northern Hemisphere during the lower-solar-activity period. The contribution of the ENSO cold phase in 2010 and 2011 to the quasi-biennial oscillation in the TEC DE3 and SPW4 amplitudes is not negligible.[Figure not available: see fulltext.].