The invention is directed to a mattress retainer system for adjustable beds which includes a mattress-retention bracket housed within a pocket of a mattress accessible in an upward direction through an opening along a bottom edge of the mattress. The pocket is formed by attaching a separate piece of material along a bottom edge of the mattress at one or both of opposite head/foot ends thereof and permitting an overlying downwardly projecting portion of a peripheral covering of the mattress to remain free thereby defining the opening into the pocket.