Toumpas initially signed a two-year contract with the Demons after he was selected with pick No.4 in last year's NAB AFL Draft.
But in a show of faith for his burgeoning talent, the Demons decided to lock Toumpas away for another year before other clubs try to prise him away from Demonland.
Demons list manager Tim Harrington said the club was excited to tie the talented Toumpas to the club until 2015.
"We’re rapt that Jimmy has seen his future at the Melbourne Football Club," Harrington told melbournefc.com.au.
"He’s infectious, has the right personality and he’s brought a lot of excitement to his teammates.
"I think the fans are going to be really pleased with what they see on field, but we also see him making a good off-field contribution, even in the early years of his career."
The 19-year-old has been a standout on the training track in his first pre-season for the Demons, and has quickly adapted to the demands of senior football.
Melbourne football manager Josh Mahoney told AFL.com.au in January, players such as Toumpas and fellow draftee Jack Viney were very much in calculations for round one.
"We're potentially going to have a different looking side in round one with a good mix of new experienced players and some draftees coming in," Mahoney said.
"It's really exciting for everyone to have so many changes."
Toumpas shone for South Australia at last year's national championships, captaining his state and earning All Australian honours for a consistent carnival.
The former Woodville West-Torrens youngster was regarded as a top two pick for much of last season - but slipped a little in the pecking order- where the Demons pounced with their first-round selection.
Melbourne kicks off its NAB Cup campaign against North Melbourne at Etihad Stadium at 6:45pm, before facing Richmond immediately after.
Jimmy Toumpas is a midfielder in NAB AFL Fantasy. He did not play in 2012. Register your team at our AFL Fantasy Hub.
Follow AFL Media reporter Ben Guthrie on Twitter at @AFL_BenGuthrie
