They will join head coach Randy Carlyle's staff for the 2014-15 season.
Horachek, 54, served as head coach of the Florida Panthers last season after being named interim coach on Nov. 8. In 66 games under Horachek, the Panthers posted a 26-36-4 record.
The Stoney Creek, Ont., native served as head coach of the American Hockey League's (AHL) San Antonio Rampage at the beginning of the 2013-14 season before his appointment with the Panthers. He also spent nine seasons as an assistant coach with the Nashville Predators (2003-2013), serving his last two years as associate head coach.
Spott, 46, served as head coach of the Toronto Marlies during the 2013-14 season, posting a 45-25-6 record and leading the team to the AHL's North Division title and a berth in the Western Conference Final.
The Toronto native previously spent 12 seasons with the Kitchener Rangers of the Ontario Hockey League, first as an assistant to Peter DeBoer then as a head coach.
Spott has also served on the coaching staff of Canada's under-18 and under-20 teams and was head coach of Team Canada at the 2013 world junior hockey championship in Ufa, Russia.