Forbort came of age during his junior season at Duluth East High School in Minnesota with 28 points in 21 games before joining USA Hockey's National Team Development Program.

After Forbort had 14 points (four goals, 10 assists) during his first full season with the USNTDP, he began his freshman season at the University of North Dakota in 2010-11 with 15 assists in 38 games. It was during his collegiate years when Forbort began attracting attention as a two-way defenseman. He was ranked No. 9 on NHL Central Scouting's final list of North American skaters for the 2010 NHL Draft and was chosen by the Los Angeles Kings with the No. 15 pick.

Forbort signed a three-year contract with the Kings on April 5, 2013, and spent two full seasons with Manchester of the American Hockey League before making his NHL debut on Oct. 16, 2015. He established himself as a full-time NHL player by appearing in all 82 games in 2016-17 and 78 in 2017-18, finishing each season with 18 points.