This study reports on a facile and economical synthetic method to prepare nano molybdenum by solid-state reaction technique. Metallic nano molybdenum was synthesised from molybdenum trioxide, molybdenum IV oxide and molybdenum VI oxide through thermal decomposition technique. Metallic nano molybdenum prepared from molybdenum IV oxide was used to study the catalytic effect of molybdenum nanoparticles on the growth of Anabaena sp. The increase in concentration of nano molybdenum from 0.1 to 100% in BG11 (N⁻ Mo⁻ + nano Mo) medium increases heterocyst frequency. The chlorophyll and protein content in Anabaena sp. was found to improve when compared with bulk molybdenum particles and showed a positive influence to be used as a nano nutrient for Anabaena sp.