Studies of radiation damage in magnetoplumbite-type LaMgAl11O19 and CeMgAl11O19 are reported. Ion irradiation was conducted on ceramic composites containing a LaMgAl11O19 phase at 500°C with 10 MeV Au+ ions and on ceramic composites containing CeMgAl11O19 phase at 800°C with 92 MeV Xe+ ions. The radiation response of these similar LnMgAl11O19 (Ln = La and Ce) hexaaluminate magnetoplumbite phases was evaluated using transmission electron microscopy (TEM) and X-ray diffraction (XRD). LaMgAl11O19 was amorphized by 10 MeV Au ions with swelling of the structure within an approximate 2 μm radiation depth from the irradiation surface. CeMgAl11O19 did not amorphize after 92 MeV Xe-ion irradiation, but ion track damage contrast is seen in approximately 5 μm of the irradiated depth. SRIM Monte-Carlo simulations of nuclear displacements correlate with the experimental results.