A 1997 graduate of Boston University, Hynes was a three-year letterman for the Terriers as a forward and participated in four straight NCAA Frozen Four tournaments.

In 1995, Boston University captured the 1995 NCAA Division I National Championship in front of Hynes' home crowd in Providence, Rhode Island.

[2] Hynes also led the U.S. under-18 national team to three medals at the IIHF World U18 Championships, gold in 2006, silver in 2004, and bronze in 2008.

On June 2, 2015, Hynes was named as head coach of the New Jersey Devils of the National Hockey League (NHL), replacing Scott Stevens and Adam Oates.

[10] On January 7, 2020, Hynes was named as head coach of the Nashville Predators, replacing Peter Laviolette.