CHI picked up the business, which was previously held by Miles Calcraft Briginshaw Duffy, without a pitch.
MCBD parted company with the directories business earlier this month.
CHI was handed the account by Thomson Directories' newly appointed chief executive, Max Alexander.
Alexander joined Thomson in March this year, replacing Linda Pancratz.
He was previously the managing director of Talk Talk, an account that CHI also holds.
He said: "I had a great experience working with CHI at Talk Talk, where we grew our customer base from 100,000 to two million. So it was an easy choice to work with the agency again on the Thomson Local brand."
MCBD had handled the Thomson business since 2004. The agency is now involved in the pitch for the £20m Yell account, a direct rival to Thomson. The Yell business moved out of Abbott Mead Vickers BBDO in April.
Thomson's media account is handled by The Media Shop, while Dare handles its digital account.
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