The private couple, who recently announced that they're expecting their first child, have been romantically linked for just over a year, and have managed to have no shortage of sweet moments in that time.
Keep reading for all the ways the pair shows their love for one another.
"I'm very happy at the moment, it's a good holiday right now. It's a good Christmas this year," he said. "You know, it's a very good holiday this year. I've had my birthday -- Oct. 30 -- so I get sort of Halloween, Thanksgiving, Christmas, it's been perfect this year and that's all I can say."
Also in December, Dewan stepped out to support Kazee's performance in Love Actually Live in Los Angeles. At the time, an eyewitness told ET that Dewan sat near the front row during the performance at The Wallis Annenberg Center for the Performing Arts, adding that she teared up during a few scenes. At curtain call, Dewan was seen smiling and applauding from her seat and, at the very end, Kazee blew a kiss, the eyewitness says.
At the after-party, ET’s eyewitness revealed that Kazee came into the room and approached Dewan from behind. The two hugged and shared a smooch. The eyewitness said that after the kiss Dewan wiped her lipstick off Kazee’s face. Kazee was also seen hugging Dewan’s mom, Nancy Lee Bursch, and her step dad, Claude Brooks Smith, was also there.
While typically very private about her relationship with Kazee, Dewan did share how her 43-year-old actor beau made her into a massive WWE fan.
"Steve, my boyfriend, is a huge wrestling fan and he got me, like, so into it. So much that I watched WrestleMania by myself," Dewan, 38, told Cena. "He wasn't even in town and I watched WrestleMania  because I had to know if Becky Lynch was going to beat Ronda Rousey. I was by myself, I ordered it... I was sitting there, like texting [him], 'Do you know what's happening?' I had to! I had to know. I was hooked!"
ET's Keltie Knight spoke with Dewan in August in the midst of her preparations for Soundtrack, an upcoming modern-day musical drama series for Netflix, and she revealed that Kazee had been "very helpful" with her latest venture, thanks to his Broadway background, which includes a Tony Award for his role in Once.
"You know what, he did give me some little tips and hints there, because it was my first musical experience," Dewan said, adding that "things are great" with her man.
In an Instagram post announcing her pregnancy, Dewan gushed over Kazee, calling him "a gift from above."
"Becoming a mother is quite simply the absolute best most incredible thing that has ever happened to me 💕," Dewan said, referencing Everly, her 6-year-old daughter with Tatum. "... I couldn't be more excited to be expanding our family together."
Kazee's post about Dewan's pregnancy news spotlighted his girlfriend's "love, warmth, and kindness" while praising her for handling "some of the hardest moments life can deal you with grace, humility, and a desire to learn from the ups and downs."
In addition to his obvious love for Dewan, Kazee also celebrated Everly in his sweet note.
"Jenna also brought with her one of the greatest gifts one could ever imagine...her beautiful daughter," he wrote. "Evie burst into my life like a supernova and has continued to burn so brightly in it."
"I have learned so much about parenting already from watching how amazing Jenna is with her," he added. "And Evie has taught me so much about what it means to love and communicate with a child and I can’t wait to give her a sibling and make our little family a little bit bigger."
For more with the happy couple, check out this video: