O'Loughlin, 35, and his girlfriend, model Malia Jones, are expecting their first child together, E! News reports. Both the actor and Jones, a former United States Amateur Surfing champ, each have a child from previous relationships.
O'Loughlin is currently filming Season 3 of the CBS cop drama, which will introduce his character's mother, played by Christine Lahti, this coming year.
The new season of Hawaii Five-0 premieres on Monday, Sept. 24 at 10/9c on CBS.