Brigden has spent 10 years managing UK search businesses while I Spy Search is in its third year of existence.
The agency's founder Chris Whitelaw has moved to the role of president, but the role of managing director Nick Jones, who joined in February 2007, will not change.
Brigden was managing director of The Search Works for three years after joining in 2004, and was promoted to chief executive shortly before it and company group The Technology Works were bought by TradeDoubler in 2007 for £56m.
Until 2004 he was Northern Europe sales director at Overture, a role he held for four years.
Whitelaw said: "Search continues to defy gravity as it moves into the boardroom and having Jim on board gives us the firepower and experience to accelerate our market share."
I Spy doubled headcount to 42 last year and won paid and natural search clients including Avon, QVC and Tesco.