The stars grace a double cover in the magazine's February issue. Mendes is pictured on the front wearing a sky blue dress followed by a second cover featuring Lachey in a button-down shirt and jeans.
Lachey, 33, had a 2006 hit album, "What's Left of Me," which used his broken marriage with Jessica Simpson as inspiration.
"I've certainly gotten my share of criticism from people who are like `how could you talk about all that? It's so undignified,"' he says in an interview with the magazine.
"For me, it was the greatest thing I could do to let my guard down and be willing to expose my emotions and put them into music. Especially when going through an experience like divorce, you have to find some outlet to get that out of your system or it'll eat you up."
Mendes, 28, has starred in films such as "Training Day" and "Hitch," and will be seen opposite Nicolas Cage in the thriller "Ghost Rider," a Sony Pictures release, which is slated to open in theaters Feb. 16.
"I took a risk with acting. ... You just always have to take risks," she tells the magazine. "I always go with my gut, and it's always right. People are scared to do that."