We investigate the scattering efficiency of carriers with optical phonons in Landau‐quantized graphene within a microscopic theory. Strong carrier–phonon scattering is induced, if the transition energy between Landau levels is in resonance with the constant energy of the respective optical phonon mode. Here, we study the phonon‐induced scattering rate as a function of magnetic field and temperature. Our results reveal a generally enhanced scattering rate for higher magnetic fields, which is peaked at the magnetic field fulfilling the resonance condition. Furthermore, we find a slower phonon‐induced relaxation at higher temperatures due to phonon occupation effects leading to a stronger increase of the scattering rates for phonon absorption in comparison to the phonon emission.Sketch of the energetically lowest Landau levels with the Dirac cones for vanishing magnetic field in the background. The optical excitation with linear polarized light (yellow arrows) and the phonon‐induced transitions (green arrows) are illustrated.