A surprised Blackburn won 55% of the vote to beat the odds-on favourite and former "It Girl".
He has won a large sum from the show for the National Autistic Society.
Former drug addict Palmer-Tomkinson has raised a smaller sum for London's Chemical Dependency Centre, representing her lower share of the audience vote.
Admitting being away from his family had been the hardest part of the fortnight, Blackburn said he had found an "inner peace" in the jungle.
"I found something I had in me that I didn't realise I had before.
"The last couple of days I had wanted to win very much. It's one of the best things that's ever happened to me."
Low point
Blackburn had won over viewers with his calm presence as fellow minor celebrities bickered incessantly in front of the cameras.
Revealing his secret, he added: "I saw the others blowing their top the whole time and I didn't want to let my family down."
"Being older it does give you a certain maturity."
Tara Palmer-Tomkinson said her low point on the show was when she tried to escape.
"I just thought 'what am I doing here, it is clear that something's wrong and I seem to be irritating people' and I didn't have that much confidence in myself."
Palmer-Tomkinson confessed she had propositioned entertainer Darren Day but denied passing notes to him in the hotel before the move to the jungle, as he had said.
She said: "There was one thing I wrote on my hand. My parents are watching, I'm not going to tell.
"I was flirtatious, I put my hands up to that."
The 1.5 million votes cast was the highest of the series and ITV will be hoping Sunday night has bettered the highest average viewing figures of 8.3 million for the eviction of entertainer Darren Day.
Christine Hamilton, wife of disgraced Tory MP Neil, was voted off the ITV reality show on Saturday.
Explosive rows
Hamilton said she had been frustrated by getting so close to winning only to be voted out.
She told ITN on Sunday that she had acted to calm down the explosive rows that had afflicted the camp in the Australian Outback.
"There were some amazing emotional fisty-cuffs which I'm sure were hugely entertaining to watch.
"There were some explosive characters there who, frankly, wherever they had been were always going to let rip at each other.
"I saw my role as peacemaker."