Per The Daily Mail, the couple was spotted in London on Monday, pushing a double stroller while shopping in Hampstead. The actors have yet to confirm the birth of their second baby.
Hartnett and Egerton have been together since 2012 and welcomed a daughter in December 2015. The pair slyly confirmed they were expecting a second child while attending the Vanity Fair Oscars party earlier this year, where the 28-year-old actress looked stunning in a black, body-hugging dress that showed off her growing baby bump.
During an appearance on Live With Kelly and Michael in April, the Penny Dreadful actor gushed about his baby girl.
"Your ego melts away when you have a new kid," said Hartnett. "Your heart kind of leaves your body and you give it permission to walk around with someone else for a while. It's really terrifying but it's beautiful. I love it more than anything. I wish I would have started it earlier. But I'm so glad that she is the one I'm raising."
For more on the couple's first child, watch the video below
ET has reached out to the couple's reps for comment.