An epoxy matrix of Carbon Fiber Reinforced Plastics (CFRP) was modified using sub-micron Cross-linked acryloNitrile Butadiene Rubber (CNBR) particles to improve the mechanical properties of CFRP. The static tensile strength increased more than 15% in comparison with the strength of unmodified CFRP when the rubber content was 10 wt%. The Young's modulus little changed due to CNBR modification of the matrix. Fracture toughness and fatigue crack propagation resistance under Mode I loading were also improved due to CNBR modification. The impact resistance in the flat-wise direction was improved as well. Fatigue lives under tension-tension loading were significantly extended by CNBR modification at all stress ranges, although the slope of the S-N line of CNBR modified CFRP is almost the same as that of unmodified CFRP. Differences in fractured surface and internal damage accumulation process between two CFRPs were found. Fatigue lives also increased for hole-notched specimens due to CNBR modification.