In this study, the effect of nano-SiO2 (up to 25 wt%) on the mechanical properties of an anhydride cured epoxy resin was investigated with particular attention on the fatigue crack propagation behaviour (FCP). The Young's modulus showed good agreement to the Halpin-Tsai predictions for contents up to 15 wt%. The addition of silica nanoparticles evokes an increase in fracture toughness (up to 74%). However, the augmentation of the critical stress intensity factor rises with respect to the filler loading, although no linear correlation is found. Additionally, a plateau-like behaviour is observed for the fracture energy release rate at filler contents above 15 wt%. The FCP behaviour is improved in all three regimes of fatigue crack propagation. Particle debonding in combination with subsequent plastic void growth and shear yielding of the matrix are identified as major energy dissipating mechanisms in all three regimes of FCP. (C) 2015 Elsevier Ltd. All rights reserved.