A bear bag is used in Philmont because of the frequency of bears and other animals entering campsites and eating food and other scented items. Any foods or even water bottles that have contained fruit drink mix in them at any time are placed within the bags including toothpaste and soap. The idea is if the bears cannot reach the items, they will not be tempted to venture too close to the camp and thus will not be a danger to humans or themselves. A bear bag is accompanied by an oops bag.

Lightweight nylon stuff sacks are often used for bear bags with the food items placed within. These bags are generally distributed at base camp by the commisary to the crew. While some crews will choose to carry the bbags empty and distribute the food amongst themselves, most others will simply keep the food in the bags and change who is carrying them every day. Many crews choose to carry only lunches, breakfasts, or suppers in certain bags, though some may organize them by day number. Bear bags are used in conjunction with a bear bag line and rope, along with often a carabiner. The rope is first made into a bight at the center and tied, then thrown over the bear bag line or treebranch if a line is unavailable. The bight is lowered to the ground, attached to the bags, and then raised, after which the ends of the rope are tied to separate bags. Bear bags are issued at the base camp commisary at the beginning of the trek, and returned at its conclusion along with the rest of the Crew Gear.