We have synthesized thin multiwalled carbon nanotubes (t-MWNTs) using a catalytic chemical vapor deposition (CCVD) method with FeMoMgO catalyst. The number of tube walls were 2similar to6 with the corresponding diameters of 3similar to6 nm. We obtained high production yield of over 3000 wt % compared to the weight of the supplied catalyst. These t-MWNTs revealed the intermediate structural characteristics between single- and multiwalled carbon nanotubes (SWNTs and MWNTs). Critical issues for high yield synthesis of t-MWNTs were further discussed in terms of reduction procedure, growth time, and gas species.