Watts stepped out in New York City last week to see Schreiber in his new Broadway play, Les Liaisons Dangereuses, at the Booth Theater, where the actress smiled for photographers before watching the performance.
Speaking with ET's Lauren Zima at a junket promoting her new drama, Shut In, on Saturday, Watts opened up about why she feels it's vital to show her ex as much support as possible.
"He's the father of my kids," said Watts. "So it was important to support him."
"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," they told ET in a joint statement at the time. "It is with great love, respect, and friendship in our hearts that we look forward to raising our children together and exploring this new phase of our relationship."
Despite their split, Watts said that it's easy to come out for Schreiber's performances, as he's "an extraordinary talent."
"I was very curious to see this and all of his work," she added. "The play is fantastic and really I hope everyone gets to see it because he does some extraordinary work up there."
In Watts' new, tense drama, Shut In, the 48-year-old actress plays Mary, a grieving mother whose husband was killed and son paralyzed in a freak accident that devastated her family. The actress said her own experiences as a mom helped her form and shape her character.
"I am a mother and I know what it is to be a mother. I know the challenges and the struggles and the guilt," Watts explained. "[Your kids] take up all your focus and you just want to do the best by them. And that's what Mary's trying to do as well."
Shut In -- co-starring Oliver Platt, Charlie Heaton and Jacob Tremblay -- hits theaters Nov. 11.