The couple joined a crowd that included The Duke and Duchess of Cambridge and David Beckham on Wednesday (8 July) to watch the quarter final match between Andy Murray and Vasek Pospisil.
Josh was seen greeting Prince William with a handshake when rain briefly delayed play.
The Pearl Harbour actor is preparing to become a first-time father after announcing last week that long-time girlfriend Tamsin is pregnant with their first child.
Josh and Tamsin have been together around four years but have largely kept their relationship away from the spotlight, rarely appearing at red carpet events together.
They met on the set of movie The Lovers.
Josh can currently be seen in horror series Penny Dreadful, while British actress Tamsin is best known for her role in the St Trinian's movies.