This study investigates the effect of nano carboxylic acrylonitrile butadiene rubber (CNBR-NP) on the tensile fatigue behaviour of carbon fibre reinforced polymer composites (CFRP) with dicyandiamide-cured epoxy matrix. The stress-controlled tension-tension fatigue behaviour at a stress ratio of R=0.1 was investigated for CFRP with neat and nanorubber-modified epoxy matrices with CNBR-NP loadings of 5, 10, 15, 20 phr. The normalised test data revealed that the high cycle fatigue lifetime of the epoxy resin modified with 15 phr of CNBR-NP was increased twice relative to the neat epoxy resin. Scanning electron microscopy (SEM) images of the fracture surfaces showed that the improved plastic deformation and energy dissipation at the fibre-matrix interface contributed towards the enhanced fatigue life of the CFRP.