To secure an oil and gas supply, China has built several types of energy infrastructure near its borders and developed energy cooperation with regional partners based on this infrastructure. However, not all energy cooperation projects develop at an equal pace or are equally successful. This study employs the neofunctionalist spillover hypothesis—one of several key discourses applied to explaining European integration—to account for the difference in regional cooperation between two China-driven energy megaprojects in Asia: the China–Central Asia Pipelines and the China–Southeast Asia Pipelines. After investigation into the so-called spillover hypothesis, including “functional spillover,” “political spill-over,” and “cultivated spillover,” the more successful of the two projects was also found to be more significant in terms of its spillover effect. Thus, this article finds that regional cooperation in the Chinese context also supports the spill-over hypothesis, which has conventionally been regarded as a Europe-based discourse.