Jack won a tight vote count on Friday night, collecting 553 votes ahead of former Geelong ruckman Shane Mumford (545), and former Hawthorn midfielder Josh Kennedy (542).
The victory was a huge surpise to Jack, who until round 18 had been no closer than 7th in the voting and trailed Shane Mumford by 85 points.
Jack said winning the club's best and fairest was his biggest achievement and took a light-hearted pot shot at departing coach Paul Roos.
"This hasn't been easy, it's been a battle," he said.
"The coach said to my face: 'You're too small and you will never make it in AFL'."
Roos was quick to sing Jack's praises before he was announced the winner.
"Kieren's effort is exceptional," Roos said.
"His want and his desire is exceptional. When you see someone like Kieren at the footy club and you see his desire ... I genuinely believe the best player for the year was Kieren."
Jack's ferocious tackling was evidenced throughout the regular season and in the finals campaign, when he introduced Carlton skipper Chris Judd to the ANZ Stadium turf in uncompromising fashion.
Jack, 23, led the club in tackles in 2010, was ranked third overall for kicks, fourth for disposals, third for contested possessions and second for inside 50s. He also booted 21 goals.
Mumford polled outstandingly considering he missed two games after being suspended for tangling with former teammate Gary Ablett. The big man also missed a week with a knee injury.
Alongside his third placing in the overall count, Kennedy earned the Paul Roos Award for best player in the finals series.
In other news on the night, the Swans staged a tribute for retiring coach Roos and captain Brett Kirk.
Kirk marked the end of an era by imploring his clubmates to "continue to take care of and look after each other" before embracing Roos and declaring as Adam Goodes handed him the AFLPA Captain of the Year Award that "it's all about the love."
Other awards
The Paul Kelly Players' Player Award - Adam Goodes
Rising Star Award - Dan Hannebery
Dennis Carroll Trophy for Most Improved Player - Mike Pyke
Barry Round Trophy for Best Clubman - Ted Richards
Paul Roos Award for best player in the finals series - Josh Kennedy
Top 10 in the 2010 Bob Skilton medal
1. Kieren Jack - 553 votes
2. Shane Mumford - 545
3. Josh Kennedy - 542
4. Jarrad McVeigh - 497
5. Heath Grundy - 495
6. Adam Goodes - 464
7. Nick Malceski - 460
8. Brett Kirk - 455
9. Ryan O'Keefe - 444
10. Daniel Hannebery - 418
