However at the conclusion of his initial two-year contract with Melbourne, he accepted the opportunity to join the newly established GWS Giants in 2012 on a six-year deal.

Scully was presented with the number 31 guernsey made famous by club and league legend Ron Barassi.

[9] Scully finished the season by coming second in the AFL Rising Star, behind Sydney's Dan Hannebery.

He won the Harold Ball Memorial Trophy, for being Melbourne's Best First Year Player, and finished eighth in the Best and Fairest.

[11] Melbourne retrieved compensation picks for losing Scully, they traded for Dominic Barry and selected Jesse Hogan.

After signing a four-year extension with the club midway through the 2016 season,[14] Scully helped the new franchise finish fourth on the ladder and reach its first finals series in its short history.

[15] Known as "The Running Machine,” Scully received a second straight All-Australian nomination in 2017 and finished with 15 goals for the year.

Scully's frustration with the Giants' handling of his injury and the need to free space in salary cap led to the former number one pick being traded to Hawthorn.