Last month, it was reported that the couple, who have been in a relationship since 2007, welcomed their first child together in August. While neither Paul nor Zoe commented on the news at the time, the actor has now confirmed they welcomed a daughter "eight weeks ago".
"She's gorgeous, by the way. What a beautiful, beautiful little baby. How does it feel to be a dad?" host Jimmy Fallon asked the star during Wednesday night's (October 24) episode of his show.
"I'm so tired and I'm so in love," replied Paul. "It's so extreme. Your heart has gone like supernova in one sense. And then we landed from London last week and she cried for like 24 straight hours and you kind of just want to walk through a wall. It's crazy."
Paul did not share his daughter's name or exact birthday. But he did speak about his Ruby Sparks co-star Zoe and how they worked together on the screenplay for Paul's feature directorial debut, "Wildlife".
"I decided, 'You know, let me take a stab at a first draft,'" he shared of his decision to have a crack at writing the screenplay. "I've never written and I didn't know if I could, so I started dipping my toe in that pond. And as I was writing, I started thinking, 'You know, this is pretty good.' So, I gave it to my partner, Zoe, who's a proper writer, she's written plays and screenplays and she tore it apart."
Paul went on to explain that Zoe wrote her own draft of the story and they then proceeded to trade notes back and forth between them.
"We never wrote together because that was not sustainable," he laughed.