Jena announced the happy news on Instagram with photos from their first week as parents, writing that their new son, who was born on May 8, is "everything I never thought I wanted."
The actor, 31, is seen in a hospital ward with her looking down at his first child in a series of photos.
In another picture, she gently places her hand on her baby son's body, and her child's tiny hand grips her finger in another.
A snapshot of my first week with our safe handsome little king,' Jena captioned the photo. I am so thankful that my life now has so much more meaning. I'm completely smitten with this little boy; he's everything I didn't realize I wanted.
‘I'll always love you, @jasonderulo.'
'The best day of my life was taking our baby boy (Jason King Derulo) home,' Jason wrote on Instagram. He's extremely fortunate to have such a good, loving mother.'
Jena's due date was kept a secret when they announced Jena's pregnancy, instead telling fans that baby Derulo is 'coming soon.'
'Couldn't be more excited for this new chapter of our lives,' the singer said, referring to the couple as 'mum and dad.'
The pair has been dating for over a year and made their relationship public in March when they were photographed together on a dinner date.
With their innovative – and daring – workout videos attracting large audiences, they quickly became TikTok superstars.