The Game of Thrones stars, who met while playing on-screen lovers Jon Snow and Ygritte, are already parents to their nearly two-year-old son, whose name has not been publicly released.
Harington admitted he was “terrified” but excited for the new arrival during an appearance on The Tonight Show with Jimmy Fallon on Friday night (3 February).
He snuck in the happy news while talking about his son, who he said is “too smart”, adding: “He is about the get the shock of his life, which is that he’s about to get a brother or sister.”
Fallon appears surprised by the news as the audience starts clapping and cheering, and asked: “Are you serious? Pregnant?”
Harington confirmed that he and Leslie were indeed expecting and shook hands with Fallon as the late night show host congratulated him.
Asked if he was feeling nervous or excited, Harington answered honestly: “I’m terrified.
“You know with the first baby, you’re like, walking on clouds and dancing through fields and daisies for nine months?” he said, before adding: “Well, the man is anyway.
“This time, the reality check comes much shorter and you get practical, like, real quick.”
The 36-year-old actor said that while he and Leslie have tried explaining to his toddler son that they will be welcoming a new baby soon, he “doesn’t quite conceptually understand it just yet”.
“We are trying to get him ready for it and we point at Rose’s belly and we say, ‘Mummy’s baby, mummy’s baby’, and he points at his tummy and goes, ‘My baby, my baby’,” Harington said.
Harington and Leslie married in 2018 at Rayne Church, in Kirkton of Rayne, where the bride’s monk father Chad Boulton conducted the service. The ceremony was attended by their Game of Thrones co-stars Sophie Turner, Emilia Clarke and Peter Dinklage.
They welcomed their son in February 2021, with a representative for the couple describing the pair as “very, very happy”.
Last year, Leslie opened up about first-time motherhood and pushed back against the “narrative” that they should be “automatically enamoured” by their children immediately after birth.
Speaking to Harper’s Bazaar, she questioned why that should be the case “when you have never experienced having a child”, adding that being able to share the “trials and tribulations” of new motherhood with a community of other people was a “glorious thing”.