The first-time coach and his talented teen pop singer took the stage during Tuesday's finale results show.
The first-time coach -- who has already signed on for season 24 -- took the stage with his last-standing Team Niall finalist, 19-year-old Gina Miles, during Tuesday's live results show, and the pair blew the crowd away with their performance of Billy Joel's "New York State of Mind."
"Every time I get drunk, I sing it at karaoke," Niall joked of the track, as the pair promised to "slay" their performance.
And slay they did, in coordinated black ensembles in front of a cityscape backdrop, earning a standing ovation from the crowd and their fellow coaches.
ET spoke with Niall ahead of Monday's finale performance show, where he opened up about becoming fast friends with longtime Blake Shelton this season -- and bidding him farewell as he departs the show after 23 seasons.
"We're gonna have a few drinks, no doubt," Niall said with a smile. "I'm gonna miss him. Big time. I've made a real friend."
"Like, I didn't know the guy in October of last year, but he's just been a constant. We text every day. He's been a laugh the whole [time]," shared the singer. "I hope he doesn't win it! But I'm gonna miss him."
The Voice will return this fall for season 24.