Carbon nanowires with a diameter of 40–60 nm were synthesized by coating single-walled carbon nanotubes (SWCNTs) in an intermittent, one-stage DC arc discharge process. Transmission electron microscopy shows that these nanowires consist of a SWCNT with an amorphous carbon coating, whose thickness depends on the time of arc discharge. The mechanical properties of blocks of these nanowires were tested by load–unload cyclic compression and static force thermomechanical experiments. The results show that carbon nanowire blocks exhibit better compressive behavior than pure SWCNTs blocks, and carbon nanowires show a typical nonlinear strain–temperature response due to the amorphous carbon layer. A mechanism of adsorption-controlled growth of amorphous carbon on the SWCNTs in the vapor phase is proposed for the formation of the nanowires.