A day in the life of Quincy, a 5-year-old labradoodle that traveled to the U.S. Open with his owner, the tennis player Danielle Collins, sounds like something out of a Hollywood film.

He wakes up to a skyline view of New York City from the penthouse of a five-star hotel. A chauffeur takes him to Flushing, Queens, where excessive coddling and belly rubs await. Chefs prepare a plate of bacon and eggs for breakfast, and salmon for lunch. And after a hard day of work, in which he mostly watches Ms. Collins practice, a professional massage therapist works on his worn-out muscles so he can do it all again the next day.

“He’s very spoiled,” Ms. Collins, an American player who came into the tournament ranked 61st in the world, said in an interview. “I treat him like a prince.”

Professional tennis players travel the world with a team that typically consists of a coach, a fitness trainer, family and friends. Some add in a four-legged companion, typically with less specific duties. For Ms. Collins, Quincy is an essential member of her team who accompanies her virtually everywhere she goes on the grounds at the U.S.T.A. Billie Jean King National Tennis Center.

The U.S. Open is the most pet-friendly grand slam, according to several tennis players interviewed by The New York Times, making it an opportune two weeks for players to enjoy their pet’s company in a city with more than half a million licensed dogs.

All players’ pets are credentialed with their headshot printed on a blue U.S. Open badge attached to a blue lanyard — just like the ones often seen dangling from players’ tennis bags. As such, they have access to most of the spaces used by players.