AbstractLayers of dayside ionospheric plasma have been sporadically observed on Mars at 90 km altitude. Several causes for these layers have been proposed. Here we test the hypothesis that solar energetic particle (SEP) events produce these layers. Several independent lines of evidence show that SEP events do increase plasma densities at low altitudes. We compare the occurrence of low‐altitude plasma layers to a proxy for the flux of solar energetic particles at Mars. For the ionospheric layers, we use 71 instances of low‐altitude plasma layers found in 5,600 electron density profiles acquired by Mars Global Surveyor. For the proxy for solar energetic particle flux, we use the flux recorded in the highest energy channel of the Mars Global Surveyor Electron Reflectometer. We find that these low‐altitude plasma layers are not significantly more likely to occur during SEP events.