Ni-matrix-nanocomposite films were produced by constant-current electrodeposition from a sulphamate bath. The composite consisted of a disordered array of Ag-coated SnO2 nanowires grown onto a substrate by chemical vapour deposition, around which the Ni matrix was electrodeposited. The thermal stability of the films was analysed by non-isothermal annealing at up to 600°C and isothermally at 300 and 500°C for 10h, at high vacuum (10−7 to 10−6mbar). Pure Ni films were also analysed for comparison purposes. The microstructural evolution of the samples was characterised by means of X-ray diffraction and scanning electron microscopy assisted by electron backscatter diffraction. The composite showed higher thermal stability, evidenced by an increase of only 70% in its average grain size after annealing at 500°C, against the 300% observed for the pure Ni films, as a result of pinning of the matrix's grain boundaries by the Ag–SnO2 phase. Moreover, it retained its random crystallographic orientation, while Ni samples evolved from a <100> towards a <111> fibre texture due to surface energy minimisation.