The She's All That star and husband Daniel Gillies welcomed their second child, son Theodore Vigo Sullivan Gillies, on Saturday, 4 April.
Rachael confirmed the news via Twitter, linking to an article on E! News about the birth with the caption: "Welcome to the party Little Buddy. We love you so much!"
The couple are also parents to daughter Charlotte, nearly two.
Rachael and Daniel – who appears in Vampire Diaries - announced the pregnancy in January, saying they were "happy [and] surprised by this wonderful news."
Meanwhile, it's been rumoured that Rachael's iconic teen movie She's All That could be getting a Hollywood remake. Read our list of reasons why we're not sure about that here...
For exclusive competitions and amazing prizes visit Reveal's Facebook page NOW!