Space-borne SiGe-based electronics are confronted with high-energy particles and may suffer from displacement damage effects. Here, primary radiation damage of a strain-engineering-based SiGe/Si heterostructure was investigated by molecular dynamics simulations in two cases of independent and overlapping collision cascades. The results showed that among 1 keV, 3 keV, and 5 keV primary knock-on atoms (PKAs) of Si and Ge, 3 keV Ge PKAs generated the most point defects at the heterointerface, which was associated with adequate PKA energy dissipated around the heterointerface. Meanwhile, the Frenkel pairs at the heterointerface continued increasing merely in the first three cascades and tended to annihilate subsequently, whereas the antisites both in the whole heterostructure and at the heterointerface accrued from the first to the fifth cascades. In addition, the spatial distribution of point defects surviving in each collision cascade was dominated by the melting region, and it could be superimposed on the subsequent ones during the overlapping cascades. Overall, this work explored the evolution of the defect and temperature as well as the overlapping effects during the collision cascades in a strain-engineering-based SiGe/Si heterostructure, which shall shed light on radiation effects of SiGe/Si heterostructures and pertinent radiation-hardening techniques of SiGe-based electronics.