Modern cities face many problems that affect their residents' quality of life. Key issues include overpopulation and congestion, environmental pollution, lack of green spaces, inadequate waste management, climate change, inadequate infrastructure, social inequality, and public health issues. These problems are expected to intensify in the coming years. Today, cities account for almost 50% of the world's population and generate 80% of the global GDP. These percentages are only expected to rise as more people move into the cities. Organizations such as the International Organization for Standardization (ISO) and the International Telecommunication Union (ITU) develop standards that help cities address the issues they face, promoting sustainable practices and improving the quality of life for their residents. These standards include the ISO 37100 series on sustainable cities and communities (International Organization for Standardization. ISO 37100 series: Sustainable cities and communities. ISO/TC 268). Although sustainable development is a global challenge, strategies to achieve urban sustainability are largely local. Therefore, strategies vary in scope and content from country to country and region to region. To support national strategies and local initiatives in Greece, the Hellenic Organization for Standardization (ELOT) provides Greek versions of the international standards: ELOT ISO 37101, “Sustainable cities—Management systems for sustainable cities– Requirements with guidance for use” (Hellenic Organization for Standardization, ELOT ISO 37101: Sustainable cities—Management systems for sustainable cities—Requirements with guidance, 2018a) and ELOT ISO 37100, “Sustainable cities—Terms and definitions of concepts” (Hellenic Organization for Standardization, ELOT ISO 37100: Sustainable cities—Terms and definitions of concepts, 2018b). These standards help Greek cities meet international obligations and achieve Sustainable Development Goals. Furthermore, to support the sustainability strategies of municipalities, local communities, and stakeholders, and to transform Greek cities into sustainable, smart, resilient, and climate-adaptable ones, the Hellenic Organization for Standardization (ELOT) developed the standard ELOT 1457, “Sustainable development in cities—Indicators for sustainability” (Hellenic Organization for Standardization, ELOT 1457: Sustainable development in cities—Indicators for sustainability, 2018c). This standard through the development of performance indicators covers the essential functions for cities to consistently and inclusively provide quality services, ensuring a high quality of life and an attractive environment for citizens, visitors, and investors. The present study presents a summary of the ELOT 1457 standard as well as ELOT's participation in the development of new standards.