The sizes of the economies and population of the Next Eleven countries are anticipated to surge in the next couple of decades whereby their energy demands can be assumed to rise in tandem. However, meeting the rising energy demand with the traditionally-consumed unclean energy resources can impose adverse environmental consequences. As a result, achieving environmental sustainability has become an utmost important issue for these countries. Against this backdrop, this study examines whether improving energy efficiency rate, enhancing renewable electricity production, and promoting financial inclusivity can help the Next Eleven countries reduce their carbon dioxide emissions. Overall, the findings reveal that energy efficiency improvement and greater renewable electricity shares in total electricity outputs mitigate carbon dioxide emissions in the long run. Contrarily, financial inclusion, economic growth, and international trade are observed to boost carbon dioxide emissions. Moreover, energy efficiency and financial inclusion are found to jointly inhibit emissions whereby the mediating and moderating effects of energy efficiency on the financial inclusion-carbon dioxide emissions nexus are verified. Furthermore, these findings are robust across alternate estimation techniques and also when total greenhouse gas emissions are considered as an alternative proxy for measuring environmental well-being. Accordingly, several relevant environmental sustainability-related policies are recommended to the concerned governments.