A pH above 9.0 was essential for the formation of wurtzite zinc oxide (ZnO) in aqueous solution systems. The addition of complexing agents to decrease the deposition rate was required for the direct growth of ZnO on the surface of substrates through heterogeneous nucleation. The nucleation of the crystals was promoted by undercoats derived from zinc acetate. Wurtzite ZnO films consisting of hexagonal columns with diameters of 20–100 nm were successfully prepared on various substrates under suitable conditions.