14YT alloy (Fe–14Cr–0.25wt%Y2O3–0.4wt%Ti) with 4at% Sc addition was previously reported to exhibit a nanoscale microstructure and high strength when annealed at temperatures up to 1000°C (0.65Tm) for 1h. Here we report that the microstructure and mechanical behavior of 14YT–4Sc alloy after long-term annealing for up to 60h at 1000°C. FIB analysis shows abnormal grain growth with annealing time, while a large fraction of the matrix still consists of nanoscale grains. TEM images reveal a slight growth of nano grains, with estimated grain growth exponent, n, to be 0.29. Sc–Ti–Y–O enriched nano oxide particles (<10nm) were observed in EDS mapping of the 14YT–4Sc–60h sample. The nano-structure retention at the high temperature of 1000°C for 60h is attributed to these complex nano oxides.