According to the Alaska Department of Fish and Game, up to 144 brown bears have been sighted on the river in a single summer with 74 bears congregating in one place at a time[4] Its entire length of 35 mi (56 km) lies within the McNeil River State Game Sanctuary, created in 1967 by the State of Alaska to protect the numerous Alaska brown bears who frequented the area.

The McNeil River State Game Sanctuary and Refuge is part of a 3.8-million-acre (15,000 km2) piece of land that is protected from hunting; the rest of this is Katmai National Park.

And while the bear population often wanders outside the protected zone their numbers have gradually continued to rise over the years.

[4] The northern edge of the refuge lies about 50 miles (80 km) south of the southern boundary of Lake Clark National Park and Preserve.

McNeil Falls has always been famous for its bear watching, and as early as 1955, when it was closed to hunting, it was featured in an article of National Geographic by Cecil E. Rhode and in the 1956 documentary The Animal World.

In addition to the main McNeil River, Mikfik Creek to the south and Chenik Lake to the north, in the refuge, also provide bear viewing.

Both Mikfik Creek and Chenik Lake offer best bear viewing in June and McNeil River does in July.

Bears feed primarily on salmon in July but switch their diet to berries and grass in late August and early September.

[4] Aside from its famous brown bears, the McNeil River Sanctuary also has moose, caribou, wolves, red foxes, wolverines, harbor seals, and bald eagles.

[7] Twelve years later, the area was further protected in a bill signed by Alaska Governor Jay Hammond and became the McNeil River State Game Sanctuary.

However, it was discovered in 1993 that a fish ladder would be constructed in the Paint River drainage, just 3 miles (4.8 km) from McNeil Falls.

Support by Alaskan governor Sarah Palin pressured the conservationists, but they were finally able to close the refuge to hunting again in March 2007.