Abstract: Interwoven carbon nanofiber yarns were prepared from the catalytic pyrolysis of methane using ferrous sulfate and graphite as catalyst precursor and substrate respectively. They were characterized by SEM, HRTEM, XRD and Raman spectroscopy. Results indicated that the yarns had a diameter of 4 - 8μm and consisted of interwoven carbon nanofibers. The catalyst particle was observed at the root of a yarn. The carbon nanofibers had a crystallite size (La) of about 5nm and the d002 was 0.340nm. The growth of the yarns complied with a adsorptiondiffusionprecipitation mechanism and the diameter of yarn was determined by the size of the catalyst particle.