Chemical vapor deposition (CVD) is a powerful method to synthesize various carbon nanostructures (e.g., carbon nanotubes). A conventional CVD process has to be carried out at the temperatures over 600°C. To extend the applications of carbon nanostructures, for example in the semiconductor industry, low-temperature synthesis processes are thus always pursued. In this chapter we review the CVD growth of carbon nanostructures at low temperatures (<450°C). These growth processes are discussed in detail with respect to the applied catalyst system, carbon source, reaction atmosphere, catalyst faces, morphology control as well as unique structural characteristics of grown products. For the low-temperature CVD growth, catalytic reaction occurring on the low index faces of a metal catalyst is a crucial issue, and the growth is rate-limited by surface diffusion. Instead of the classical Vapor-Liquid-Solid (VLS) growth mechanism, the growth mechanism at low temperatures is interpreted with a novel Vapor-Facet-Solid (VFS) mechanism. Due to their unique features, the synthesized carbon nanostructures are promising to be applied for interconnects in large-scale integrated circuits, field emission, microwave adsorption, and as the anode material of lithium ion secondary battery, etc.