A transmission electron microscopy (TEM) specimen of a titanium aluminide (TiAl) alloy was irradiated in-situ, at the IVEM-TANDEM facility, with 1 MeV Kr ions to a maximum fluence of 1.25 × 1019 ions m−2 at room temperature. The irradiated microstructure was then investigated ex-situ using advanced analytical TEM in combination with TEM image simulations and molecular dynamics (MD) simulations. The TEM examination showed that dot-like defects first formed in both the α2-Ti3Al and γ-TiAl phases of the irradiated microstructure. With increasing irradiation dose planar defects formed and propagated within the γ phase, and most of the planar defects were accompanied by the dot-like defects. The TEM image simulations and MD irradiation simulations revealed that the origins of the dot-like and planar defects were interstitial clusters and stacking faults, respectively, and large interstitial clusters were surrounded by dislocation loops. The interstitial clusters formed and grew in the irradiated microstructure due to much faster diffusion of interstitials than that of vacancies at room temperature. Local stress concentrations increased near large interstitial clusters and lamellar interfaces, which resulted in the nucleation and propagation of stacking faults. Moreover, the configurations of the lamellar interfaces in the start microstructure were found to play an important role in the formation and accumulation of the radiation-induced interstitial clusters and stacking faults at room temperature.