Herridge was rewarded for consistent performances across all three rounds of the championship - Targa High Country in November, Targa Wrest Point in January and the final round, Targa Tasmania, that started in Launceston on Wednesday and finished at Hobart's Wrest Point on Sunday afternoon.
The West Australian, who made his name on gravel with Subaru Rally Team Australia, took his WRX STI to fourth place at both High Country and Wrest Point, while his second was his biggest result on tarmac to date.
Targa Tasmania was won by Queenslander Tony Quinn in a Nissan GT-R. He finished three minutes and 39 seconds ahead of Herridge after the gruelling five-day, 500 kilometre challenge. South Australian Matthew Sims was third in another Nissan GT-R one minute 58 seconds further back.
The field that gathered for the 20th running of Targa Tasmania included seven-time Bathurst winner and eight time Targa champion, Jim Richards, V8 supercars legend Dick Johnson, reigning titleholder, Jason White, in a Lamborghini and former winner, Steve Glenney in a Mazda RX8.
Herridge was never daunted by the magnitude of the challenge, proving once again that motorsport victories require speed, consistency and reliability.
"It's been our aim to win the championship, and we thought we'd be a chance, but it's sometimes hard to have our little Subaru battling against the Lambos and the GT-Rs," Herridge said.
"We thought a concentrated effort on something like the championship would be something that would be achievable.
"After day four we decided we were happy with second in the event, which is a good solid result, and the final day was all about conserving our spot, therefore Sunday was all about getting it home and winning the championship.
"It's still a thrill to win a championship, and I'm very proud to be second in what was arguably the most competitive Targa field that has ever been assembled."
Not only did Dean take the championship title, both he and the second Maximum Motorsport WRX STI of Graham Iddles finished with their best Targa Tasmania results. (Dean in 2nd, Graham 21st).
"There's a great team of people who work behind the scenes to develop and prepare these cars and keep them running during the event. We only came with two cars this year, a smaller team than last year, but everyone's worked together and the results speak for themselves," Herridge added.
"I must also thank the co-drivers who have supported me during the championship. Glen Weston and Bill Hayes had the duties for the first rounds and Ben Searcy was fantastic this week in his first event with us."
Targa Tasmania 2011 - Final Results
1. Tony Quinn / Naomi Tillett ,  Nissan GT-R
2. Dean Herridge/ Ben Searcy, Subaru WRX STI, +03:39
3. Matthew Sims / Dennis Sims, Nissan GT-R, +05:37
4. Tony Sullens / Julia Barkley, Subaru WRX STI, +06:52