score:2
According to the National Park Service, advanced reservations are not accepted. However:
Reservations are accepted for group camping, the Colter Bay RV Park, and the Headwaters Campground & RV Sites at Flagg Ranch.
Upvote:2
The answer to this question appears to be changing in a couple of weeks, with the campgrounds moving to a reservation system.
According to the National Park Service website:
All park campgrounds that were first come, first served are moving to an advance reservation system. Campsites will be reservable for the 2021 season on Recreation.gov beginning January 26, 2021 at 8:00 a.m. Mountain Standard Time. On that date, reservations will be available for stays through July 26, 2021, and then on a rolling six-month basis thereafter. See news release and FAQs.