The two actors were photographed laughing and smiling together during a rare outing in New York City on Sunday.
Watts, 52, wore a dark blue floral printed dress and a jean jacket as she walked her dog while Crudup, also 52, wore a dark gray T-shirt, jeans, black jacket and a baseball cap as he spoke to his girlfriend.
This is a rare sighting of the two, who keep their relationship private and away from the public eye.
Watts and Crudup were first seen together in March of 2017 while heading to a sushi spot for lunch in New York City.
In July 2017, a source at the time confirmed to PEOPLE that the stars were dating.
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The two played husband and wife on the Netflix series Gypsy which debuted in 2017. In February 2018, the couple was photographed together at the BAFTAs afterparty in London.
Watts was previously in an 11-year relationship with Liev Schreiber, which came to an end in 2016. The couple has two children together: Samuel Kai, 12, and Alexander "Sasha" Pete, 13.
The former couple announced their split in a joint statement, saying, "Over the past few months we've come to the conclusion that the best way forward for us as a family is to separate as a couple."
A source on the set of Schreiber's Showtime series Ray Donovan told PEOPLE, "They have been on the rocks for quite a while."
Crudup dated actress Mary-Louise Parker until 2003. He then dated Claire Danes from 2003 to 2006.