We revisit the effect of the “Eco-Patent Commons” (EcoPC) on the diffusion of patented environmentally friendly technologies following its discontinuation in 2016, using both participant survey and data analytic evidence. Established in January 2008 by several large multinational companies, the not-for-profit initiative provided royalty-free access to 248 patents covering 94 “green” inventions. Hall and Helmers (2013) suggested that the patents pledged to the commons had the potential to encourage the diffusion of valuable environmentally friendly technologies. Our updated results now show that the commons did not increase the diffusion of pledged inventions, and that the EcoPC suffered from several structural and organizational issues. Our findings have implications for the effectiveness of patent commons in enabling the diffusion of patented technologies more broadly.