Many Belt and Road Initiative (BRI) countries are developing nations with significant potential for future carbon emissions growth, making their green transition crucial to achieving the Paris Agreement goals. This study applies a two-stage decomposition model to analyze emission drivers across income levels. Findings show that from 1987 to 2022, economic growth was the main driver of emissions, while energy intensity and carbon intensity had a mitigating effect. Low-carbon transitions in many BRI countries remain slow or have yet to begin, especially in low-income nations where fossil fuel dependence is deepening. In contrast, high-income BRI countries have shifted from coal and oil to natural gas. During economic crises, most countries relied on high-carbon energy for recovery and relaxed energy efficiency standards. The study offers policy recommendations to accelerate emissions reduction in BRI countries and highlights the importance of international cooperation.