The actress explained that their 2-month-old daughter, Esmeralda, has been keeping her up at night -- and she's loving it.
"We're getting the hang of the sleeping thing, but I'm exhausted and it's the best," she said during an appearance on "The Ellen DeGeneres Show." "I'm so incredibly tired. I thought I was tired before at times, but no, nothing like this. But I wouldn't have it any other way."
Mendes, 40, and Gosling, 34, welcomed their daughter in September. However, they never confirmed that the actress was pregnant, nor did they share the news of the baby's arrival.
"Early on we decided it's going to be so hard for her to have privacy, and we thought, 'Well, this is the first opportunity we can give her to protect her,'" Mendes explained. "So, I had a nice, calm pregnancy."
Now, she's busy taking care of her new daughter. And while she doesn't feel pressure to hit the gym just yet, breastfeeding has been helping her body bounce back, she said.
"And then obviously you want to be healthy for the baby because she's kind of eating what I"m eating," she said. "You want to make good choices."