A novel method is presented to synthesize herringbone-stacked carbon nanofibers in high selectivity using cobaltocene as the catalytic precursor. Thiophene was essential for carbon nanofiber growth while hydrogen was used as the carrier gas. Selectivity close to 100% was achieved using cobaltocene, thiophene, and hydrogen reacted at 1100°C. The conversion rate of the nanofibers collected in the cold trap was approximately 1.5 wt % of the initial products. The effect of the catalytic precursor temperature, thiophene, and acetylene was investigated, with reference to nanofiber diameter and selectivity.