Molecular dynamics simulations have been performed to investigate the effects of helium on the displacement cascades in α-iron. Besides conventional analysis tools, a new graphical representation of the data based on ternary plots has been introduced. Results show that the production of defects and their subsequent clustering appear to be greatly influenced by the presence of helium. Calculations reveal that the location of helium atoms, substitutional or interstitial, plays a major role. Compared to pure iron, interstitial helium atoms increase the amount of Frenkel pairs generated during the cascades. Conversely, substitutional helium atoms tend to decrease this production. However, in both cases, it is observed that helium atoms stabilize larger self-interstitial clusters, due to a strong binding energy. These simulations show that helium atoms trap self-interstitial clusters and would thus slow down their subsequent migration. Some helium–vacancy clusters are generated in the core of the displacement cascades but also grow at the periphery of self-interstitial clusters. It is shown that results greatly depend on the irradiation temperature.