"Paul asked who she was after seeing her give a speech," the New York Post said Morgan told Howard Stern on his Sirius Satellite Radio show Wednesday. "I introduced them. I'm not sure if Paul knew that she was missing a leg at the time."
Morgan said he was surprised Mills turned out to be a "grasping, gold-digging little bimbo."
"I was fooled into thinking that she was a good person," he laughed. "She ended up costing Paul $50 million."
McCartney and Mills married in 2002 and were officially divorced earlier this year. They are the parents of a 4-year-old daughter.
Morgan told the Post that being interviewed at length by Stern was the "highlight" of his career.
"I can die a happy man now," he said. "I've met Nelson Mandela, Princess Di, Queen Elizabeth II and Tony Blair, but this was the biggest honor."