The member states of the Organization of the Petroleum Exporting Countries (OPEC) face complex challenges in pursuing their long-term development objectives, particularly in terms of reducing greenhouse gas emissions, enhancing environmental sustainability, and managing the consequences of climate change. In this regard, the present study examines the effects of economic growth, financial development, technological innovation, and the utilization of renewable energy sources on the environmental sustainability of OPEC countries, while also considering the mediating role of trade openness. The study covers the period 2004–2023 and applies a static panel data approach using fixed-effects models. Data were collected from the World Development Indicators (WDI), and the selection of countries and time span was based on data availability. The empirical findings indicate that financial development, technological innovation, and the increased share of renewable energy have a positive and significant impact on the environmental sustainability of OPEC countries. Conversely, economic growth exerts a negative and statistically significant effect on ecological sustainability. Furthermore, trade openness functions as an important mediating mechanism, influencing the relationships between the aforementioned variables. Based on these results, the study suggests that OPEC countries should pursue pathways toward sustainable economic development. In particular, when designing emission reduction policies and environmental strategies, policymakers need to carefully account for the interplay among financial development, technological innovation, and the transition toward cleaner energy sources.