The Giants announced on Tuesday that senior players Callan Ward and Phil Davis will be co-captains into season 2013, with Scully to deputise.
Former Bulldogs defender Ward and former Adelaide star Davis were re-elected to lead by the Giants playing group and will head into the new season without the senior guidance of recently-retired champion Luke Power.
Ward, Davis and Power were the three co-captains during GWS' inaugural season in the AFL, before Brisbane premiership hero Power hung up the boots at the end of the 2012 campaign.
Scully, 21, is in the leadership group for the first time.
Scully made the lucrative move to the Giants from Melbourne at the end of the 2011 season and was immediately touted as a future captain.
The talented midfielder said the leadership elevation had taken him by surprise.
“I certainly wasn’t expecting this, but I’m very humbled to be voted by my teammates as vice captain and look forward to working closely with Phil and Callan,” Scully said in a club statement.
“Since coming to the Giants I think my leadership is something which has really improved.
"Obviously being one of the players with a bit more experience in the squad is a unique thing in itself especially being so young myself.
“I think it has helped me mature a lot more as a person and as a footballer. It’s something that I have really embraced.
"Setting an example through leadership is something I hope to develop over this year and in the years to coming.
“I’m really looking forward to the year ahead and the responsibility that comes with it.”
Giants mastermind coach Kevin Sheedy said Scully's election showed the esteem in which young playing group holds the former Demon.
"The feedback from our playing group was that Tom is a true professional who is highly respected for the way he prepares himself but also does a lot of little things that often go unnoticed during games," Sheedy said.
"Together with Callan Ward and Phil Davis they form a very talented leadership group that will help guide our exciting young playing group in their second year in the AFL."