Although a court may order custody of a child to someone other than a parent or to an agency, in making that decision, the court must first consider the presumption that it is in the child's best interests to remain with one or both parents. The natural parent's superior right to custody of a child is not absolute and must yield to the best interest of the child.

In all cases involving custody of a child, whether between a parent and step parent, between a parent and other relative, or between a parent and an agency, there is a presumption that it is in the best interests of the child to remain with the natural parent. Many states have statutes which provide a preferential order that the court should consider in making custody decision, and in those states, the natural parents of the child are listed first. Although the first choice of a court would be the natural parent of the child, the court is required to consider what is best for the child and the natural parent is not always the best choice.

Where a nonparent challenges the parent for custody of the child, it is up to the nonparent to show that the child would be better off with the nonparent. The parent may have mental problems or substance abuse problems that would impair that parent's ability to care for the child. If a child has lived with a nonparent for most of that child's life, it could be psychologically harmful to the child to abruptly change custody. The best interest of the child standard means that in some situations, a nonparent may be awarded custody of the child, even though the parent disputing custody is fit and capable of raising the child.