Objectives: The rapid growth in population, urbanization, and industrialization reduces the natural green space environment and increases air pollution on the planet. The green space environment minimizes air pollutants, and swift climate changes and provides fresh and clean air. This study investigates the prevalence of diabetes mellitus in environmentally highly green and less green countries in Europe. Subjects and methods: Based on the Environmental Performance Index (EPI) score, which rates a country's environment, 43 European countries with 760 million people were selected. The EPI score was recorded from the USA's Environmental Performance Index (EPI) website. 60% of the EPI score is based on seven categories related to ecosystem vitality: biodiversity and habitat, ecosystem, fisheries, climate change, pollution emissions, agriculture, and water resources. 40% of the score is based on four categories related to environmental health: air quality, sanitation and drinking water, heavy metals, and waste management system. The prevalence of diabetes mellitus in all 43 European countries was obtained from the International Diabetes Federation (IDF). The European countries' populations were obtained from the World Bank. We divided the countries into three groups based on each country's EPI score. The 11 countries with an EPI score of more than 75 were classified as highly green space, 24 countries with an EPI score of 50-75 were classified as moderately green space, and 8 countries with an EPI score of less than 50 were classified as less green space environment countries in Europe. Results: The mean prevalence of diabetes mellitus for highly green space environment countries was 7.49 +/- 1.53%; moderately green space countries were 8.98 +/- 2.38%, and for less green space environment countries was 9.79 +/- 3.05%. In countries with less green space (i.e., environment, EPI scores less than 50), the prevalence of DM was significantly higher than in green space countries with EPI scores of more than 75 (p = 0.041). The results revealed a negative correlation between the green space environment (EPI Score) and the prevalence of diabetes mellitus. Conclusions: The prevalence of diabetes mellitus is significantly reduced in environmentally high green space countries than in low green space countries in Europe. This means that countries with environmentally sustainable environment policies have less diabetes. It is suggested to establish strategies to keep the living environment green and clean to minimize air pollution and fight against diabetes mellitus. (C) 2022 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).