The One Direction heartthrob was rumoured to have shared a romantic tryst with the 33-year-old blonde after he joined Kimberly, her singer father and his wife Penny Lancaster for dinner in Los Angeles, California, in April.
Now Rod, 68, has "let the cat out of the bag" by revealing that Harry, 19, stayed over at his LA mansion with his daughter.
Speaking on Alan Carr's TV talk show, 'Chatty Man', Rod said:"His [Harry] car was here in the morning. Let's put it that way. But he may just have come round to pick something up."
But when Alan asked if Rod if he had any concerns about notorious ladies man Harry entering his pad, he abruptly replied: "No."
After realising his mistake, he added: "B******s! I let the cat out of the bag."
Harry - who was previously in a relationship with 23-year-old Taylor Swift - was spotted kissing and holding hands with Kimberly during the dinner they had together.
A source previously said: "They [Harry and Kimberly] weren't exactly hiding it - Rod was well aware what was going on and didn't seem to mind.
"Harry's well-known for his thing for older women, and Kimberley is a striking blonde so it's easy to see the appeal."