Addition of ZrC to ZrB2 is favored to improve the fracture toughness of ZrB2. In this paper, ZrB2-ZrC composite nanofibers with eutectic composition are fabricated by electrospinning and carbothermal reduction. The precursors prepared by electrospinning are smooth and uniform. ZrB2-ZrC composite nanofibers could be fabricated by heat-treatment of precursors at 1300 degrees C in argon. Heat-treatment temperature influences the crystalline structure and grain size of nanofibers. The diameter of ZrB2-ZrC composite nanofibers is about 250 nm. The mole ratio of ZrB2 and ZrC in the nanofibers is 47:53, very close to the eutectic composition of ZrB2-ZrC composites. Some amorphous carbon is present in the nanofibers. The effect of heat-treatment temperature on amorphous carbon content is analyzed. The interface between ZrB2 and ZrC nano-grains is characterized. (C) 2018 Elsevier B.V. All rights reserved.