Yorkshire broker Smart and Cook has acquired independent Stockton broker Lindo and Tindale.
The acquired business has annual revenue of £700,000.
The two companies would trade separately in the short term, but were expected to merge into larger premises in 2005, Smart and Cook said.
It announced the acquisition at the same time as its parent company, Thornton Grove Holdings, released its 2003 results.
Chairman Geoff Cook said the group's profits had been boosted by a series of acquisitions, including Oughtred & Harrison Insurance and Castlegate Insurance Brokers.
Thornton Grove spent £1.5m on acquisitions during 2003, and £73,471 in the previous year.
Turnover from Thornton Grove's continuing operations increased from £10m in 2002 to £13m in 2003, while operating profit for continuing operations increased from £1.3m to £2m.
The results precede Smart and Cook's deal, worth £57m, with venture capitalist 3i to fund further growth, completed in March this year.