He played college basketball for the Stony Brook Seawolves, leading the team to its first ever appearance in the NCAA Tournament and graduating as the school's all-time leader in several career categories.

After going undrafted, Warney became the first Stony Brook player to reach the NBA when he made his debut with the Dallas Mavericks on March 11, 2018.

Warney moved his career overseas and signed with the Seoul SK Knights of the Korean Basketball League before the 2019–20 season.

After not finding success at baseball, football or wrestling, he was recruited to play AAU by a friend's mother, even though Warney did not have much basketball knowledge at the time; he recalled tackling an opposing player in order to defend a layup in his second game.

With the guidance of Boff, Warney overcame a poor work ethic that resulted in low middle school grades in order to perform well academically at Roselle Catholic and remain eligible for the NCAA.

During his junior year, Warney faced St. Patrick's Catholic player Michael Kidd-Gilchrist, a future second-overall draft pick from Kentucky, in the playoffs and put up 20 points and 11 rebounds.

[4] Warney was originally expected to accept a scholarship to play college basketball at nearby Rider, but Stony Brook head coach Steve Pikiell and his assistant Jay Young continued to heavily pursue him through a connection with Stony Brook player Bryan Dougher, who had played on the same AAU team before Warney.

Once Iowa's interest was publicized, Warney earned attention from roughly 25 schools, including Villanova, Notre Dame and Tennessee.

However, Warney wanted to play immediately instead of redshirting or being a bench player at a power conference school, and he was drawn to Stony Brook during his official visit.

[1] Ranked as the number five recruit in New Jersey by EKB Scouting and the 49th-best power forward in the country by ESPN, Warney officially committed to Stony Brook on August 12, 2011.

[3][5] Warney made his collegiate debut in Stony Brook's season opener on November 9, 2012, against Marist, recording eight points and five rebounds.

[6] In his second game against Mount Ida, Warney scored 16 points on a perfect 8-for-8 from the floor, becoming the first Stony Brook player in program history to attempt at least eight shots and make them all.

After the game, Huskies head coach Jim Calhoun visited the Stony Brook locker room to personally praise the 18-year old Warney.

[10] Stony Brook was eliminated in the semifinals of the America East tournament to Albany, losing 61–59 on a last-second layup.

[12] Against Iowa in the second round, Warney led Stony Brook with 17 points and seven rebounds, but the Seawolves lost 75–63 and ended the season with a 25–8 record.

[14] Warney won his first America East Player of the Year award during the 2013–14 season, averaging 14.5 points, 8.0 rebounds and 1.2 blocks per game while shooting .616.

[20] In the CBI opening round against Siena, Warney had 15 points and 10 rebounds, his tenth double-double of the season, and a new career-high five blocks.

[21] Warney repeated as America East Player of the Year for the 2014–15 season, averaging 16.7 points, 11.7 rebounds and 2.5 blocks per game, leading the conference in all of those statistics.

[22] Despite a Warney double-double, Stony Brook lost in the America East championship game to Albany again, this time on a last-second Peter Hooley three.

[28] He was named as a finalist for the Lou Henson Award, an AP honorable mention All-American, a NABC All-District Team selection and first-team All-Met.

With 29 points against Northeastern, Warney overtook Bryan Dougher (1,609) to become the top scorer in Stony Brook's Division I history.

[2] In a loss to Albany, Warney surpassed Emeka Smith (1,978), a Division III player from 1989 to 1993, to become Stony Brook's all-time leading scorer.

[39] He was named to the 35-man midseason watch list for the Naismith Trophy and one of the final five finalists for the Karl Malone Award, given to the best power forward in the NCAA.

Stony Brook won the America East regular season title for the second time in Warney's career with a 14–2 conference record.

[42] In the quarterfinals of the 2016 America East tournament, Warney scored 27 points and grabbed a career-high 23 rebounds in an 86–76 win over UMBC.

[74][75] Warney played with the senior United States national team at the 2017 FIBA AmeriCup, where he won a gold medal.