And the gesture worked – with Andy emerging triumphant, winning over two sets by 6-4 6-1.
It was a very different story from the last time Kate watched Andy play on Centre Court.
The Duchess could hardly hide her disappointment as Andy lost out in the Wimbledon final to Roger Federer.
This time the brunette royal looked delighted, applauding with her husband as Andy emerged triumphant at the All England Club.
Kate looked elegant in the electric blue £515 Stella McCartney dress which she recently wore for an exhibition opening at the National Portrait Gallery.
She teamed it with her new Smythe navy blazer with gold buttons that she has worn to two Olympic events already this week.