Fresh off signing a contract extension last Friday, Gardiner played a key role in the Lions' scrappy 23-point win over Melbourne at Etihad Stadium on Sunday.
The 191cm backman took a career-high 12 marks opposed to Jack Watts, Chris Dawes and James Frawley.
He also collected 18 possessions – which he used at an elite 94 per cent efficiency – to earn the Rising Star gong.
"That was one of the pleasing bits of it my ball use was a lot better than it has been at times, especially getting a bit more of it than usual," Gardiner told AFL.com.au.
"The way Melbourne played allowed us to get a bit more involved as defenders."
The 18-year-old becomes the third Lions cub to receive a Rising Star nomination this season after James Aish in round six and Lewis Taylor in round nine.
The diminutive Taylor, 19, and Gardiner were recruited from the Geelong Falcons via draft picks the Lions received for the "Go Home Five", who requested trades at the end of last season.
In a major boost to the rebuilding club, the duo have followed fellow 2014 draftee Nick Robertson by putting pen to paper on new deals tying them to the club until the end of 2016.
The 2012 class of Marco Paparone, Sam Mayes and Michael Close have also been locked away to multi-year deals.
Gardiner, the Lions' second pick at No.22 overall last November, said it was a relatively simple decision to extend his stay in Queensland.
"You have a little think about it. But there wasn't much hesitation there once they put something out to us," he said.
"I was pretty happy to get it done and move on."
The versatile big man wasted no time proving his worth after making his debut in round five against Richmond.
The Lions plunged to a 0-5 start, but Gardiner has helped tighten up a leaky defence in his 13 games.
He's averaged 11 disposals and four marks and played in five of the Lions' six wins.
"We're pretty happy with how we've gone after that start to the year," Gardiner said.
"For the second half of the season we're just trying not to get blown out like we were in that first half towards the end of games.
"We'd run out of puff so it's been good to show how we've improved over the course of the season.
"With all those contract extensions - there's been a few throughout the year with the younger boys - I reckon everyone's pretty excited about the next couple of years."
