The best interests of the child refers to the factors most courts consider when making decisions on child custody and visitation rights.

These factors may include the needs and circumstances of the child (happiness, security, mental health, emotional development, educational opportunities, special needs, siblings, religious and cultural considerations, continuity and stability, child’s wishes) and the circumstances of the parent or caregiver (relationships, living arrangements, history of abuse, mental health, physical health, financial resources, substance abuse).

There is generally a presumption that it is in a child’s best interests to have a relationship with both of the child’s biological parents—unless one or both of the parents are shown to be unfit parents.

In Washington State, the 'best interests of the child' standard is the guiding principle for courts when making decisions regarding child custody and visitation rights. This standard takes into account various factors that affect the well-being of the child, including but not limited to the child's safety, emotional growth, health, education, and the need for a stable environment. The court also considers the child's relationships with siblings and each parent, the child's wishes (especially if the child is of sufficient age and maturity), and any history of domestic violence, substance abuse, or other behaviors that might impact the child's welfare. Washington law does presume that maintaining frequent and continuing contact with both parents is in the child's best interest, provided that both parents are fit to care for the child. However, this presumption can be overcome if evidence is presented that contact with a parent would be detrimental to the child's physical, mental, or emotional health.