<p>This paper considers a green product supply chain where a manufacturer invests in green Research and Development (R&amp;D), an e-commerce platform implements data-driven marketing and holds private demand information, and a third-party agency provides eco-label certification. The manufacturer chooses between adopting a third-party label (3P label) or a self-label, while the platform decides whether to share demand information with upstream supply chain members. We develop a multi-stage game-theoretical model to investigate the strategic interaction between platform information sharing and manufacturer eco-label selection. The findings indicate that under the 3P label, the platform is willing to disclose demand information when the manufacturer’s green investment efficiency is relatively high. Interestingly, under the self-label strategy, improving green investment efficiency does not motivate the platform to share information, as information sharing severely aggravates the double marginalization effect. Our results also indicate that improving demand forecast accuracy will motivate the manufacturer with high efficiency to adopt the 3P label, whereas stronger consumer trust in the self-label will induce the manufacturer with low efficiency to select the self-label. In addition, an unexpected result shows that, for the manufacturer with high efficiency, a moderate reduction in investment efficiency may actually improve profit under the 3P label. Finally, several extensions are provided to examine the strategic variations in platform demand information sharing and manufacturer eco-label selection, and additional insights are obtained.</p>