The objective of this study is to investigate the association between military spending and environmental sustainability within the N-11 countries. There exists a strong correlation between sustainable economic expansion and energy consumption, which in turn results in the generation of elevated levels of carbon emissions. Moreover, it is plausible that a correlation exists between military spending and the degradation of the environment. The primary objective of this study is to examine the emissions of carbon and emissions of greenhouse gases in the N-11 countries, as these nations exhibit comparatively elevated levels of such emissions. Therefore, this study examines the correlation among economic growth, militarization, renewable energy, and environment in the Next Eleven nations from 1990 to 2022. The cross-section autoregressive distributed lag (CS-ARDL) model is employed to analyze the enduring and immediate connections between variables. Empirical evidence indicates that a country’s environment is positively influenced by GDP and militarization. The escalation of military capital intensity has exacerbated the environmental damage. Increasing the adoption of renewable energy sources can mitigate negative environmental impacts over time. This study proposes policy recommendations for sustainable development, including reducing militarization and improving the use of clean energy.