Hydrazone polymers were prepared by the diazo coupling reaction of bisacetoacetamides with diazonium salts under mild basic conditions. Bisacetoacetamides 1 and 2 having two 1,3-diketo groups were prepared by the reaction of aromatic diamines with diketene. Diazonium salts 3-5 were prepared by the reaction of aromatic diamines with nitrous acid in an aqueous HCl. A diazonium salt was isolated in a stable form after exchanging chloride with fluoroborate. The resulting polymer structure was determined by spectroscopic methods to be mainly polyhydrazone. The hydrazone unit was found stabilized by the intramolecular hydrogen bonding. The polymer obtained from 2 and 5 was soluble in organic solvents and showed the UV maximum peak at 376 nm in dimethyl sulfoxide.