The effects of MoO₃ addition on the carbothermal reduction of fine TiO₂ were studied for obtaining nanopowders and for understanding the mechanism of the carbothermal reduction. TiO₂ was mixed with C powder and MoO₃ powder. The mixed powder was heat treated in a rotary tube furnace up to 1773 K. The results indicated that the particle size of TiO₂ – MoO₃ – C powder heated in the rotary tube furnace was comparable to that heated in batch-type furnace. The CO gas concentration during the carbothermal reduction of TiO₂ – MoO₃ – C powder was measured. It was confirmed that the reduction temperature of titanium oxide decreased with an addition of MoO₃.