The 39-year-old, who shot to fame as Seth Cohen on "The O.C.", and Leighton - who starred as Blair Waldorf on "Gossip Girl" - wed in 2014 after dating for four years, and welcomed daughter, Arlo Day in 2015.
Leighton plays Angie in the ABC show, and her off-screen hubby will be appearing as musician Derek - who has previously romanced her character - in the finale of the ABC show.
"Single Parents" debuted last year (18), and follows a group of adults navigating single parenthood with their young kids.
Speaking to Glamour about her new show, Leighton revealed that she can relate to her character, even though she's not a single mother.
"Angie is a paralegal and a mom and has very little time to do anything," the 32-year-old explained. "We use comedy on the show to explore co-parenting and being single parents. I can only imagine it is the hardest job in the world, because being a parent is the hardest job in the world."
The actress, who has kept her motherhood journey private and away from the spotlight, opened up about the struggles of being a first-time parent.
"Nobody can tell you what parenthood is going to be like," Leighton shared. "You think you know, and then it's just so hard. I feel so, so lucky that I have help and a husband. I feel stable, but there are so many people who don't have that. In a really tender way, 'Single Parents' explores how parenting is an emotional roller coaster."