The authors revisit the effect of the “Eco-Patent Commons” (EcoPC) on the diffusion of patented environmentally friendly technologies following its discontinuation in 2016. 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. In previous work, Bronwyn Hall and Christian Helmers (2013) suggested that the patents pledged to the commons had the potential to encourage the diffusion of valuable environmentally friendly technologies. The updated results in this paper now show that the commons did not increase the diffusion of pledged inventions, and that the EcoPC suffered from a number of structural and organizational issues. The authors hope these findings will inform future efforts to make environmentally friendly technologies more broadly available for use.