Abstract Atmospheric tides produce a well known pronounced longitudinal wavenumber‐4 (WN‐4) structure in the ionosphere, but their influence on electromagnetic‐wave propagation through the ionosphere remains poorly constrained. Here we use DEMETER satellite measurements to show that the extremely low frequency (ELF) electric field in the low‐latitude topside ionosphere contained a robust daytime WN‐4 pattern during 2006–2010. The seasonal variation of the WN‐4 amplitude is consistent with the reported climatology of the diurnal eastward‐propagating tide with zonal wavenumber 3 (DE3). The meridional phase structure of WN‐4 is in‐phase between geomagnetic low‐latitudes and the magnetic equator, indicating that the pattern is unlikely to be imprinted by the F‐region ionosphere but is rather driven by the tidal modulation of lower‐ionospheric attenuation during the trans‐ionospheric propagation of ELF waves. These results suggest a coupling pathway by which lower‐atmospheric tides can modulate the trans‐ionospheric propagation of ELF electromagnetic waves.