Pets are permitted in Rocky Mountain National Park, however they are NOT permitted on trails or in the backcountry. They are allowed only in areas accessed by vehicles, including roadsides, parking areas, picnic areas and campgrounds. They must be kept on a leash no longer than six feet and attended at all times. Pet etiquette dictates always cleaning up after your pet and disposing of waste in trash receptacles.
Dogs and cats are considered to be unnatural predators in a natural environment. Pets may harass and even kill wildlife, carry disease and intrude on other park visitors' experiences. Pets are also prey for larger carnivores like mountain lions and coyote packs.
Do not leave pets unattended in vehicles. Interior temperatures of vehicles rise within minutes and pets can quickly overheat and die, even with the windows cracked. Pet boarding facilities are available in Estes Park and Grand Lake.
The Arapaho-Roosevelt National Forest does allow leashed pets on trails and in the backcountry. Contact them directly for details and specific locations.