3C-SiC nanowires with nanosheets were synthesized via a direct reaction of Si vapor (from solid silicon) and SiO vapor (from silicon and silicon dioxide) with graphene nanosheets at 1500 °C without any additional metal catalyst. The resultant products were characterized by XRD, SEM, TEM and room-temperature photoluminescence (PL) spectroscopy. The results indicated that the product comprised SiC nanowires with nanosheets. The nanowires were mainly composed of curvy aggregated wires with diameters of 30–80 nm, some representative straight whiskers with a pellet at their tips, and some distinctive structures including connected particles, a dumbbell shape with dense stacking faults and periodic twins with screw dislocations. The nanosheets present in the products were thin SiC polycrystalline multilayers within a few nanowires. A combined VLS and VS mechanism was proposed for their formation. The PL spectra of the resultant SiC nanowires with nanosheets indicated a remarkable blue shift in comparison to the bulk SiC, implying their great potential applications in optoelectronic devices.