The methanation kinetics of CO over a bimetallic catalyst containing 6Co:1Mo:4K:100SiO2 has been studied and compared with that over a 6Co:4K : 100SiO2 monometallic catalyst. Nine models arising from carbide, enolic and Eley Rideal mechanisms were considered and assessed with respect to the rate data obtained for each catalyst. Interestingly, all three models which were considered statistically adequate involved the dissociative adsorption of H2 as the rate-determining-step (RDS). The modelling results also suggest that the introduction of Mo to Co altered the methanation behaviour of CO over cobalt kinetically but not mechanistically.