In the following weeks, a tournament to determine a new champion was arranged, in which Alexander defeated Gran Metalik in the first round, TJP in the quarterfinals, and Roderick Strong in the semi-finals to advance to the final. At WrestleMania 34 on April 8, Alexander defeated Mustafa Ali to win the Cruiserweight Championship. On the following episode of "205 Live", Alexander was attacked by Buddy Murphy during his championship celebration. At the Greatest Royal Rumble event, Alexander made his first successful title defense against Kalisto. Alexander then retained his title against Murphy on the May 29 episode of "205 Live" and against Hideo Itami on the July 10 episode of "205 Live". At SummerSlam, Alexander successfully retained his title against Drew Gulak. On the September 19 episode of "205 Live", Alexander defeated Gulak in a SummerSlam rematch to retain the Cruiserweight Championship. At Super Show-Down on October 6, Alexander lost the Cruiserweight Championship against Buddy Murphy, ending his reign at 181 days, and also marking his first televised loss in 2018.