Since the role of fiscal decentralization cannot be overlooked in tracking sustainable development goals targets of a clean environment and climate mitigation, it is inevitable to understand the comprehensive picture of its link with environmental quality. Unlike past studies, this study investigates the combined influence of energy prices and non-linear fiscal decentralization on carbon emissions in the presence of institutional quality and gross domestic product in the model. It employed advanced econometric panel techniques on data from 1990 to 2018 for the top seven fiscally decentralized Organisation for Economic Co-operation and Development (OECD) nations, including Spain, Belgium, Austria, Switzerland, Germany, Australia, and Canada. The main outcomes are as follows: first, a cointegrating equilibrium link is existent among the study variables. Second, the linear term of fiscal decentralization promotes carbon emissions, while the non-linear term mitigates it. It verified the inverted U-shaped curve between fiscal decentralization and carbon emissions. Third, increasing energy prices for non-renewable energy decrease carbon emission due to a substitution effect. Among other explanatory variables, improvement in the quality of institutions decreases carbon emissions, while the gross domestic product increases it. These findings suggest strengthening fiscal decentralization, lowering non-renewable energy prices, and improving institutional quality to check the deteriorating environmental quality in the study sample and other worldwide regions.