Smith and Lovato, both 27, shared a release date, Friday, and a promo photo for the song, titled "I'm Ready," and its music video Monday on Instagram.
The photo shows Smith and Lovato wearing matching white athletic wear and gold medals.
"I'M READY @ddlovato YOURS APRIL 17th," Smith captioned the post. "Incredibly happy to release this song with my gorgeous and talented friend. I love you Demi!! Can't wait for you all to hear it THIS FRIDAY xx."
Smith also shared their excitement in an interview with ET Canada published Monday.
"Growing up listening to her music and singing her music and trying to sing like Demi Lovato, I've been training for this moment for a long time. I absolutely adore her," the singer said.
"As well as her incredible talent, everything she stands for as a human being is what I believe in and I just adore her," they added. "So, I'm happy it's worked and I hope this isn't the last time we sing together."
Smith said they asked Lovato to appear on the track in the wake of her 2018 overdose and hospitalization.
"I'd been in contact with Demi for the last few years and before music or anything, I wanted to reach out to her as a friend and that's what I did," Smith said. "She came to the studio and she's in an amazing place. She's the strongest person I've ever known."
Smith announced in March that they will will rename their third studio album, originally titled To Die For, and delay its release due to the coronavirus pandemic.