On September 22, 2015, Warrick signed with Melbourne United for the 2015–16 NBL season. After averaging 12.8 points per game for United off the bench over the first five games, helping the team earn a 5–0 start, Warrick sustained a groin injury and was placed on the short-term injury waiver list. He was temporarily replaced in the line-up by Garrett Jackson on October 29, returning from injury on November 22 to face the New Zealand Breakers. On February 17, 2016, he was named NBL Best Sixth Man for the 2015–16 season. Warrick helped lead United to the minor premiership after finishing the regular season in first place on the ladder with an 18–10 win/loss record. However, in their semi-final series against the fourth-seeded New Zealand Breakers, United were swept 2–0 to bow out of the playoffs. In 23 games for United in 2015–16, Warrick averaged 14.2 points and 6.0 rebounds per game.