| Tortoise Group | NV |
| Trevor Zoo | NY |
| Trout Unlimited | VA |
| Trout Unlimited (Oak Brook Chapter) | IL |
| Trout Unlimited Virginia | VA |
| Tucson Audubon Society | AZ |
| Tuolumne River Preservation Trust | CA |
| Turner Endangered Species Fund | MT |
| Turtle Island Restoration Network | CA |
| Union of Concerned Scientists | DC |
| Unitarian Universalist Ministry for Earth | OR |
| Unitarian Universalists for the Ethical Treatment of Animals | VT |
| United Church of Christ EcoAction | TX |
| United Plant Savers | VA |
| Upper Missouri Breaks Audubon Society | MT |
| US PIRG | DC |
| Vermont Audubon Society | VT |
| Vernal Pool Association | MA |
| Vet Voice Foundation | OR |
| Virginia Forest Watch | VA |
| Virginia Herpetological Society | VA |
| Virginia Society of Ornithology | VA |
| VOICE for Animals | ME |
| Voices of Wildlife in NH | NH |
| Walker Lake Working Group | NV |