While The Jungle Book movies show Baloo teaching Mowgli "The Bare Necessities" in song and generally how to be carefree, the Baloo of the book is a much more serious character. He is so serious and reliable that the Wolf Pack entrusts Baloo to teach all of their cubs about the Law of the Jungle.

Readers find out about Baloo's role early in the book when the pack is trying to decide if the man's cub (Mowgli) will be allowed to stay with the pack. Akela wants to know if any wolf will vouch for the cub, but no wolf does. Baloo speaks up and says to let Mowgli be a part of the pack since the boy poses no threat. Baloo even says that he is willing to teach the boy.

I speak for the man’s cub. There is no harm in a man’s cub. I have no gift of words, but I speak the truth. Let him run with the Pack, and be entered with the others. I myself will teach him.

Later, we are told that the "big, serious, old brown bear" that is Baloo loves teaching Mowgli because of how quickly Mowgli acquires the knowledge that Baloo teaches. Baloo's main job is to teach Mowgli the Law of the Jungle, but Baloo gets to teach Mowgli so much more than he would teach the wolves. The wolves only have to learn enough of the law as it pertains to the pack, but Mowgli has to learn much more. Baloo teaches Mowgli the Wood and Water Laws as well. Mowgli even has to learn the Strangers' Hunting Call. Baloo is adamant that Mowgli learn everything even though Bagheera questions the necessity of it.

“Better he should be bruised from head to foot by me who love him than that he should come to harm through ignorance,” Baloo answered very earnestly.