This paper reports the development of a novel carbon fiber with isotropic pyrolytic carbon core via isothermal-isobaric catalyst-free CVD of propylene. The morphological and microstructural characterizations of the carbon fibers developed were carried out by polarized light microscopy, scanning electron microscopy and transmission electron microscopy. Both the elastic modulus and hardness of the two components of these carbon fibers were measured using nanoindentation technique. The results show that the isotropic pyrolytic carbon core has a homogeneous and complex microstructure, which accounts for approximately 64% of the whole carbon fiber volume. It is this unique core structure that enables these carbon fibers to possess excellent overall mechanical properties with nearly isotropic performance in both the axial and radial directions. (C) 2015 Elsevier B.V. All rights reserved.