| Difference Makers Media | IL |
| Desert Fishes Council | CA |
| Delaware Riverkeeper Network | PA |
| Delaware Ecumenical Council | DE |
| Delaware Center for Inland Bays | DE |
| DC Natives | DC |
| Darby Creek Valley Association | PA |
| CU Wildlife Club | CO |
| Creature Conserve, Inc. | RI |
| Creation Justice Ministries | DC |
| Cougar Rewilding Foundation | WV |
| Cosmic Sister | MA |
| Cosley Zoo | IL |
| Cornell Greens | NY |
| Conservation Northwest | WA |
| Conservation Law Foundation | ME |
| Conservation Fisheries | TN |
| Conservation Council for Hawai'i | HI |
| Conservation Alliance of the Great Plains | NE |
| Conservancy of Southwest Florida | FL |
| Connecticut Association of Conservation and Inland Wetlands Commissions | CT |
| Coastal Plains Institute | FL |
| Coast Range Association | OR |
| Coalition on the Environment and Jewish Life | NY |
| Citizens United for Animals | WI |
