ET's Carly Steel caught up with the star at Paramount's presentation during CinemaCon 2018 at The Colosseum at Caesars Palace in Las Vegas on Wednesday, and Cena got very candid about his big breakup earlier this month.
"There's no other way to say [it]," the WWE star shared. "I love Nicole with all my heart, and that's that."
The pro-wresting power couple -- who got engaged after a tag team match at WrestleMania 33 last April -- revealed their decision to call it quits in a statement posted to Bella's Instagram on April 15.
"After much contemplation and 6 years of being together Nikki Bella and John Cena announced today their decision to separate as a couple," the message read. "While this decision was a difficult one, we continue to have a great deal of love and respect for one another. We ask that you respect our privacy during this time in our lives."
Cena, however, is keeping his head in the game when it comes to his career. He turned out to lend his star power to this year's CinemaCon to promote his upcoming action epic Bumblebee -- a spin-off of the blockbuster Transformers franchise, focused around the titular robot in disguise and set two decades before the events of the first film.
Cena, who just celebrated his 41st birthday on Monday, plays Special Agent Burns in the film, and the star admitted that joining the mega-hit Transformers franchise has been "very exciting."
"I'm not supposed to give a lot away… [but] I think it's a wonderful um take on a franchise that the world loves and I think [fans are] gonna go on a wonderful ride with us to the origins of Bumblebee," he shared.
"It was interesting because uh we both share parallels," Cena said of Steinfeld, who has enjoyed success in the world of film and pop music. "We both come from live entertainment and we do film as well."
"I really enjoyed talking to her on set about what it's like, what her struggle is like, and what her life is like, balancing a film career and a career in live entertainment," he continued. "She's a very driven human being."
Bumblebee hits theaters Dec. 21.