The paper deals with the assessment of the carbon nanotubes (from 0.1 to 0.5 wt %) and carbon microfibers (from 0.5 to 5 wt %) influence on the fracture toughness of carbon fiber reinforced polymers (CFRP) in Charpy V-notch tests. Various content of micro- and nanofillers affects differently the longitudinal and transversal impact toughness due to different reinforcement mechanisms and development of deformation and fracture. It is obtained that application of carbon microfibers leads to the reduction of the absorbed energy, while filling CFRP with nanotubes increases longitudinal but decreases transversal toughness.