"It's happy news," Claflin said of the latest addition to their family.
"She's very new and shiny. I, however, am not," he also joked about his newborn daughter.
The fiercely private couple never officially announced Haddock's pregnancy, but there was no hiding her baby bump last October when she attended the U.K. launch of Birks Jewellery in London. Claflin and Haddock have been married since 2013.
Last year, the 31-year-old actor candidly opened up about the body shaming that he and other male actors experience in the film industry.