Carboxylate-capped zinc oxide nanoparticles are produced by a simple user-friendly solventless route. ZnO precursors are obtained by the intimate mixing of zinc acetate dihydrate and a carboxylic acid. Subsequent thermal treatment of the solid precursor at low temperature (90–120 °C) for 30–148 h leads to the elimination of the acetate as acetic acid and yields carboxylate-coated crystalline ZnO nanoparticles. The method gives excellent results with a great variety of acids, such as benzoic acid, phenylacetic acid, phenylvaleric acid or long chain carboxylic acids (f.i., lauric and 3,6,9-trioxadecanoic acids). The chemical structure of the carboxylic acid tail significantly determines several properties of the powdered nanocrystalline ZnO material, such as the morphology of the aggregates and their dispersibility in common solvents. Further, the easiness of the method to produce colloidal suspensions facilitates thin film deposition. Finally, deposited laurate-capped ZnO can be transformed into pure ZnO by short-time (15 min) UV light treatment.