The Missouri State Highway Patrol reports Donald and Nancy Lawler, both 79, were southbound on I-35 south of Pattonsburg.
Investigators say he lost control of his Cadillac, which hit a guardrail and then reentered the traffic lanes.
They were then hit by a tractor-trailer, which pushed the Cadillac into another semi.
Donald Lawler suffered serious injuries. Nancy Lawler suffered moderate injuries.