After Grandfather Mosiah led the Nephites north out of the land of Nephi, across the wilderness and into Zarahemla, he eventually turns the kingdom over to his son Benjamin. Thus ends the small plates, and now Mormon picks up on his transcription of the large plates of Nephi.

Amaleki, the keeper of the sacred plates, having no children, turns the plates over to King Benjamin. During this time, the Lamanites somehow found their way across the wilderness and fought great battles against King Benjamin and the Nephites but were driven out of the land and back to the land of Nephi.

King Benjamin had 3 sons, and one of them was named Mosiah, after his grandfather Mosiah, and it is this grandson's name from which this book is named.

This episode covers the famous teachings of King Benjamin, who emphasizes service to one's fellow beings as synonymous with serving God, inspires moral rectitude, and establishes an exemplary model of selfless leadership. Furthermore, the profound insights into the human condition, that the natural man is an enemy to God. He proclaims the necessity of the atonement through Jesus Christ and that by no other name can salvation be given. He prophesies of the coming of Christ and the need to seek forgiveness through and by His atonement as though Christ had already come.