Though the couple has yet to confirm reports that they are expecting, the talk show host seemed to suggest on Twitter that they will soon be parents.
- Ellen DeGeneres (@TheEllenShow) July 9, 2014
Reps for the couple did not respond immediately to ABC News' request for comment.
Media outlets, including People magazine, have reported that Mendes, 40, and Gosling, 33, are expecting their first child.
The pair have been together since 2011 after meeting on the set of their film, "The Place Beyond the Pines," in which they play parents.
In February, Mendes shot down pregnancy rumors during an appearance on DeGeneres' show.
"It's so ridiculous," Mendes said. "It all started because I didn't want to go through those X-ray scanners at the airport, which are really creepy. They basically see you naked, right. And not only that, but there's a radiation aspect to it. So I always opt out. I always ask for a personal pat down."