The carbothermic reductions of niobium pentoxide and pyrochlore were studied in the temperature ranges 1625–2855 K and 1520–2440 K respectively in an argon transferred-arc plasma using a single stationary pellet reactor system. The main reaction products were NbC and CO. The reaction rates were independent of the particle sizes comprising the pellets but were influenced by the contact between the oxide and carbon particles. The reduction kinetics were successfully correlated by a reaction model of the form −ln (1 − x) = KT where x is the conversion and K is an overall reaction rate constant. The level of agreement improved with increasing reaction temperature and carbon concentration. The reaction rates increased with increasing carbon-to-oxide ratio to an optimum ratio (C: Nb2O5 = 10:1) beyond which no further increase in reaction rate was observed. The apparent activation energies for niobium pentoxide and pyrochlore reduction were 50.3 and 51.4 kJ/mole, respectively. The reduction rates of the Nb2O5 were higher.