The feasibility of depositing a thin film of highly concentrated alloy on zircaloy-4 substrates at low temperatures was investigated. Electron microscopy characterisation at micro and nanoscales showed that the deposited thin film is near-equiatomic, single-phase and with all alloying elements uniformly distributed throughout the microstructure. Heavy-ion irradiations carried out in situ within a transmission electron microscope revealed the generation of both defect clusters and inert gas bubbles at around 1.5 × 1016 ions·cm−2 (15.4 dpa). Post-irradiation characterisation showed that the thin film preserved its solid solution and that, under the studied conditions, no elemental segregation or phase transformations were observed, indicating a high radiation tolerance.