The Saint was one of a record 15 first-time All Australians in the 2012 team announced in Melbourne on Monday night.
After hearing his name called out in a back pocket, Dempster credited first year St Kilda coach Scott Watters with helping him discover a more attacking side to his game.
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"It's a great privilege, something that I'll enjoy looking back on at the end of my career, and something that over the last few years I probably didn't even think was possible," Dempster said.
"Over the last few years, my way of contributing to the team was in more of a defensive role.
"Since Scott's come in, from day one he gave me confidence in the other areas of my game that I probably hadn't realised and used in the last few years."
See the list of All Australian nominees who missed out
Another first-time All Australian was young Collingwood star Dayne Beams, rubber-stamping his progression from promising midfielder to one of the elite.
He was named on the wing, with his higher-profile teammates Scott Pendlebury and Dane Swan selected on the bench.
Pendlebury said he was happy to see all three Magpies on-ballers in the line-up.
"I think it's a great credit to 'Beamsy' that he's been able to step up in [Luke Ball's] absence and not only contribute, but dominate games," he said.
"I'm really happy for him. Probably his preparation is the best that it's been [this year]. He's a lot more determined.
"Definitely in games this year I've been amazed at the things that he's been able to do."
The other All Australian debutants were Fremantle's Luke McPharlin, West Coast's Beau Waters and Nic Naitanui, Swans Ted Richards and Josh Kennedy, Hawthorn's Grant Birchall and Cyril Rioli, young Richmond star Trent Cotchin and his teammate Brett Deledio, Essendon skipper Jobe Watson, Adelaide midfielders Patrick Dangerfield and Scott Thompson, and Geelong's Tom Hawkins.
