Oxide Dispersion Strengthened (ODS) ferritic-martensitic steels are considered for nuclear applications as structural components for fusion or fission reactors. To ensure good performances in service, the stability under irradiation of the microstructure and especially of Y-Ti-O nanoclusters have to be assessed. In-situ Transmission Electron Microscopy has been performed to follow the Y-Ti-O nano-oxides dispersed in a Fe18Cr1W0.3Ti + 0.6Y2O3 ODS material under ion-irradiation at 500°C. Microstructural examinations using bright and dark field mode showed that Y-Ti-O nano-precipitates (5 nm) are still present after irradiation up to 45 dpa. However, some larger oxides seem to be more affected by irradiation at 45 dpa (creation of point defects, interface and shape modification).