Conservation and/or environmental non-governmental organizations (CE-NGOs) have recently been scrutinized about their leadership's human diversity. Increasing diversity is an ethical obligation for CE-NGOs, and could benefit them by strengthening their problem solving, fundraising, and interactions with local communities across the world. Providing statements regarding their commitments, and including biographies and photographs of their leadership on their websites can indicate a CE-NGOs' dedication to diversity. Surveying 155 transnational CE-NGOs' websites, we found 26% did not mention human diversity in the mission statement, 65% did not use the words of equity, justice or inclusion, and 84% did not acknowledge historical or current power imbalances. A connection to local or indigenous peoples was incorporated twice as much as any other aspect of diversity. The CE-NGOs that had diversity statements were more transparent than those that did not, including more biographies and photos of their leaders. Small CE-NGOs (annual expenditures <$2 million) had fewer statements and were less transparent than large (>$10 million) ones, and CE-NGOs that fund, but do not themselves engage in conservation or environmental activities, were also less transparent. Having biographies of leaders could force a CE-NGO, whatever its size or type, to ask itself whether it represents the world it works in, stimulating self-correction, as well as generating public pressure to increase diversity. Nevertheless, providing this information should not be just for public display: it must be combined with an inclusive and equitable organizational culture that allows each member of the leadership opportunity to shape decisions. • Leadership of conservation and environmental NGOs has historically been non-diverse. • We searched 155 NGO websites for statements about diversity, biographies and photos. • 26% of NGOs did not have statements, and 84% did not acknowledge power imbalances. • NGOs with diversity statements were more likely to include biographies and photos. • Biographies and photos could put public pressure on NGOs to increase diversity. [ABSTRACT FROM AUTHOR]