NXT王座
After defeating Tyler Breeze on 20 May at , Bálor received another title shot against Owens and at The Beast in the East in Tokyo, Japan and defeated Owens to win the NXT Championship. Bálor defeated Owens in a ladder match to retain the title at on 22 August. Bálor later entered the "Dusty Rhodes Tag Team Classic" tournament in August, pairing with Samoa Joe and defeating The Lucha Dragons (Sin Cara and Kalisto) in the first round, Enzo Amore and Colin Cassady in the quarter-finals, Dash Wilder and Scott Dawson in the semi-finals and Baron Corbin and Rhyno in the finals at to win the tournament. On 4 November episode of "NXT", Bálor defended the NXT Championship against Apollo Crews, but the match ended in a no contest after Baron Corbin interfered, attacking both men. Joe came out and chased Corbin away before turning on Bálor and attacking him, which ignited a feud between the two. At , Bálor defeated Joe to retain the title. On 1 April at , Bálor retained the NXT Championship in a rematch with Joe. On 17 April, Bálor became the longest reigning NXT Champion in history (the record has since broken by Adam Cole in 2020) by surpassing Neville's previous record of 287 days. On 21 April, Bálor lost the NXT Championship to Joe at a live event in Lowell, Massachusetts, ending his reign at 292 days. At , Bálor lost to Joe in the first ever NXT steel cage match in a rematch for the NXT Championship, marking his first TakeOver loss, and subsequently his first loss under his "Demon" persona. Bálor wrestled his final NXT match on 30 July, teaming with Shinsuke Nakamura to defeat Bobby Roode and Samoa Joe.