Nanomaterial testing standards play a crucial role in the international standardization of nanotechnology within ISO. These standards specify the characteristics of nanomaterials that need to be measured, as well as the methods and procedures used for conducting such measurements. This paper presents a methodology for the development of nanomaterial testing standards, which addresses raw nanomaterials and intermediate materials like composites, suspensions, films, and coatings containing raw nanomaterials. The methodology is outlined as a scenario comprising several stages towards the goal, where essential actions to be conducted in standardization are identified and integrated into the standard. Furthermore, this paper highlights the significance of these testing standards as a technical foundation for material specification and certification, with the ultimate aim of facilitating the industrialization of nanomaterials by ensuring consistent quality and enabling reliable performance.