The concept of eco-innovation addresses a reduction in negative environmental impacts and the more efficient use of resources. As an integral part of eco-innovation, green technologies are receiving increasing attention due to growing environmental concerns. Patent data are one of the measures of the output of technological eco-innovation. However, understanding the patenting of eco-innovation comes with challenges. The aim of this study is to measure the output of eco-innovation and to analyse the trends in green technologies based on environment-related patents in the world’s leading countries from 2000 to 2017. For this research, a range of data collection techniques based on patent data from leading countries such as China, Korea, Japan, United States and Germany were employed. The study provides a comprehensive overview of changes and trends in the development of environmental technologies using different domains. In particular, significant progress has been made in the areas of environmental technologies and climate change mitigation technologies related to energy generation, transmission or distribution. These technologies are closely linked to international environmental policies such as climate change mitigation and green industry transformation. The study also contributes to the literature on measuring the output of eco-innovation.