On January 3, 2018, Roode was announced to team with SmackDown Women's Champion Charlotte Flair (dubbed The Robe Warriors) in the "Mixed Match Challenge" tournament. After Ziggler vacated the United States Championship on the December 19 episode of "SmackDown Live", an eight-man tournament was set up to crown a new champion. Roode defeated Baron Corbin in the first round and Mojo Rawley in the semi-finals. On the January 16 episode of "SmackDown Live", Roode defeated Jinder Mahal in the final to win his first championship since joining the main roster. Roode would defend the title for 54 days, retaining against Rawley during the Royal Rumble kick-off show during an open challenge and Rusev on the February 6 episode of "SmackDown Live", until he lost it against Randy Orton at Fastlane, causing Roode to attack Orton out of frustration after saving him from Mahal. Roode tried to regain the title at WrestleMania 34 in a fatal 4-way match against Orton, Mahal and Rusev, which was won by Mahal. During this time, in the "Mixed Match Challenge", Flair (who had to undergo a minor teeth surgery) was replaced by Becky Lynch via fan-vote on social media, and Roode and Lynch defeated Finn Bálor and Sasha Banks. Flair returned for the finals of the "Mixed Match Challenge", which Roode and Flair lost to the team of The Miz and Asuka.