The soon-to-be parents were seen relaxing on the beach and taking dips in the ocean over the weekend.
The pregnant Hart of Dixie actress donned a strapless bikini as she worked on her summer tan that proudly highlighted her growing baby bump.
Bilson and Christensen hugged and kissed as they relaxed in the sun and sand and were even spotted splashing at one another during one of their swims.
The PDA-filled babymoon comes just days after E! News first confirmed that the adorable brunette star is expecting her first child.
The private couple, however, has yet to publicly comment on their baby news.
But that hasn't stopped Bilson from being forthcoming about her desires to become a mother.
"When I have a baby, everyone's going to be like, 'Awww, poor teen mom. Poor girl.' And Teen Mom is my favorite show," she said in Health magazine's June issue. "I know, pathetic. But it's true," she joked.
In the cover story, Bilson also opened up about her actor beau of seven years.
"He's so incredibly supportive and considerate," she gushed about Christensen.
The duo began dating in 2007 after meeting on the set of the action-packed film Jumper.
Bilson and Christensen got engaged in December 2008 but called it off in August 2010, only to reconcile three months later.