Abstract Electron and proton precipitation into the nightside ionosphere is a key process in magnetosphere–ionosphere coupling. Although auroral electron precipitation at ∼0.1 ${sim} 0.1$–10 keV is traditionally considered the main driver of auroral emissions, recent studies show that >30 ${ >} 30$ keV electrons and protons can significantly contribute to ionospheric energy deposition, especially during storms. While energetic electron precipitation has been studied extensively, the role of energetic proton precipitation remains poorly quantified. Here, we use coordinated ELFIN and DMSP nightside observations during two substorm events, resolving electron and proton precipitation spectra from ∼30 ${sim} 30$ eV to ∼MeV. We show that >60 ${ >} 60$ keV proton precipitation, consistent with curvature scattering, can have an impact on E‐region ionization comparable to that of energetic electrons. These analyses are further supported by magnetospheric observations from the Arase and THEMIS spacecraft and ground‐based incoherent scatter radar measurements from PFISR.