Stefani shared a photo of the back of the album's CD case Tuesday, revealing the record's track list and their duet.
"Look what I found lying around the house," the "Make Me Like You" singer wrote on Twitter, adding the hashtag "#ispymyname."
Other tracks on country star Shelton's latest project include "Straight Outta Cold Beer," "She's Got A Way With Words," "Came Here To Forget" and "Friends," which will be featured in The Angry Birds Movie.
If I'm Honest will become available for purchase May 20.
Stefani previously said her own upcoming album, This Is What Truth Feels Like, is partially inspired by not only her recent divorce, but also her new romance with the Voice mentor. The singer announced her new summer tour this week, highlighting Eve as her opening act for shows across the United States starting in mid-July.