<p>Targeted radionuclide therapy (TRT) is a cancer treatment method that delivers radiation to specific tumor cells, enabling efficient tumor cell killing. Radionuclides emitting short-range beta or alpha particles have previously been the primary focus. TRT approaches utilizing low-energy electrons, such as Auger and internal conversion electrons, have attracted interest because of their highly localized tumor-killing potential. ¹³⁴Ce is an imaging surrogate in the form of a ¹³⁴Ce/¹³⁴La pair for positron emission tomography (PET) imaging in ²²⁵Ac targeted alpha therapy, and it has recently exhibited promising therapeutic properties. This study employs TOPAS-nBio, a Monte Carlo simulation tool, to investigate the radiation damage effects of ¹³⁴Ce from dosimetric and DNA-scale perspectives. The DNA damage yield analysis incorporates both physical and chemical processes. In the water sphere geometry, the overall dose contribution of ¹³⁴Ce shows patterns generally similar to those of other Auger-emitting radionuclides, and ¹³⁴Ce shows damage yields per decay close to those of ¹⁶¹Tb on the DNA scale. Although ¹³⁴Ce induces fewer DNA double-strand breaks per decay in the nucleus than ¹²⁵I and ¹⁶¹Tb, it exhibits a higher double-strand break yield when normalized to absorbed dose. Such damage outcome predictions suggest that further research on radionuclide therapy using ¹³⁴Ce is worthwhile.</p>