Abstract The synthesis of early transition nanocrystals using Na BH 4 and the respective metal oxides at atmospheric pressure was studied at temperatures between 400 and 1000°C. Reaction products were analyzed by x‐ray diffraction, the crystallite size was determined after Rietveld refinement of diffraction patterns, while the morphology was analyzed by scanning and transmission electron microscopy. For all the investigated systems the lowest temperature to complete the synthesis was 700°C and the reaction occurred in three subsequent steps: (i) decomposition of Na BH 4 , (ii) formation of crystalline ternary species Na–M–O and Na–B–O, (iii) conversion of intermediary species to MB 2 and Na BO 2 . Syntheses carried out at T > 700°C only caused coarsening of the powders. The synthetized boride powders had the morphology of highly agglomerated nanocrystals. TiB 2 had a specific surface area of 33.5 m 2 /g and crystallite diameter of 12 nm. Both ZrB 2 and HfB 2 had a platelet‐like morphology with crystallite diameter around 45 nm and specific surface area of 25.0 and 36.4 m 2 /g, respectively. Finally, NbB 2 and TaB 2 powders had a crystallite diameter around 5 nm with specific surface area of 21.1 and 11.4 m 2 /g, respectively. The goal of this synthesis is the use of cheap raw materials and moderate temperature conditions.