Molybdenum (Mo) and Cobalt (Co) play an important role in nitrogen (N) metabolism of grain legumes. Their applications to alkaline soils have been scarcely studied. A field experiment was set up to evaluate the Mo and Co application in common bean cv. Canario Centenario under two fertilization systems: inorganic fertilization and inoculation with Rhizobium etli. In each system, Mo and Mo+ Co were applied by seed impregnation at doses of 1.36 g/kg of seed for Mo and 0.26 g/kg of seed for Co; a control for each fertilization system and an absolute control were included. Yield components, nodules characteristics and N content by grains and foliage were evaluated. A completely randomized block design with seven treatments and five replications was used. Mo application increased the grain yield, grain size, nodulation and N accumulation in grains under both fertilization systems. Mo increased the total N uptake by the plant in 35.4% and 26%, for N fertilized and inoculated plants, respectively. Co application increased only nodules number and weight, and N content under inoculation. Mo application to beans cultivated in alkaline soils is recommended, but Co application is suitable only when beans are inoculated with rhizobia.