Beilein, who was born in Rochester, New York, is the second child and oldest of three sons of John and Kathleen Beilein. He was born on March 23, 1983, which he says was the day before his father began a nine-year stint at Le Moyne as head coach. He is an alumnus of Benedictine High School in Richmond, Virginia.
Beilein served as a graduate assistant for the 2008–09 and 2009-10 Michigan Wolverines men's basketball teams. While a graduate assistant at Michigan, he pursued a graduate degree at the Horace H. Rackham School of Graduate Studies. He then served as an assistant coach to Paul Cormier for the, as the director of basketball operations for the, and as the head men's basketball coach at NCAA Division II West Virginia Wesleyan College from 2012 to 2014. The position at West Virginia Wesleyan College in Buckhannon, WV was just an hour from Morgantown, WV, where Beilein had played collegiately for his father. He succeeded Jim Boone at West Virginia Wesleyan. At West Virginia Wesleyan the team improved from 12–15 during his first season to 20–12 in his second year. Beilein interviewed for the NCAA Division I head coaching job at Marist before becoming a player development coach for the 2014–15 Utah Jazz under Quin Snyder. Beilein became the head coach at Division II Le Moyne in 2015. At Le Moyne, his first game was a 2015 exhibition matchup against his father's Michigan Wolverines at Crisler Center that was attended by 70 relatives. The 15 head coaches in the Northeast-10 Conference, elected Beilein as the 2016-17 conference Coach of the Year. That season, he led Le Moyne to the number 1 seed and the host in the NCAA Division II East Regional. The team was upset in overtime by Merrimack College. In 2018, Le Moyne went on a 12-game win streak, their second longest in program history. The team went on to earn the Northeast-10 Conference Southwest Division's top seed in the 2018 Northeast-10 Conference Tournament. They won the 2018 Northeast-10 Conference Tournament. They earned a number one seed in the NCAA Division II East Regional, marking the first time an NCAA DII school has hosted an NCAA regional as a number one seed in consecutive seasons since Bentley University in 2007 and 2008. He repeated as Northeast-10 Conference Coach of the Year. Le Moyne's March 10 victory over Thomas Jefferson University established many records and firsts: It marked the team's 25th win of the season, which surpassed the 24-win mark established in 1988 and tied in 1996; It marked the school's 1000th victory; It marked Le Moyne's first NCAA tournament opening round victory since a 1964 win over Youngstown State University and the school's first NCAA tournament victory since a 1988 consolation game victory over Kutztown University. The school's March 11 victory over The College of Saint Rose earned the school its first NCAA tournament regional championship game birth, which they won. The 24th ranked Le Moyne Dolphins lost to 11th ranked West Texas A&M University on March 20 in the Division II quarterfinals, finishing the season with a school-record 27 wins against 7 losses. In March 2019, Beilein was hired as head coach for the Niagara Purple Eagles men's basketball. However, on October 24, 2019, just weeks before the beginning of the season, Beilein resigned for "personal reasons", with assistant coach and former Duke standout Greg Paulus named as his replacement on an interim basis.
Personal
Beilein has two younger brothers, Mark and Andrew, and an elder sister, Seana Hendricks. He and his wife, Kristen, had a son, Thomas Patrick Beilein, on March 25, 2018.