Windsor-based consumer specialist EHPR has been acquired in a deal with an initial consideration of £2.3m in cash and shares, but the earnout means the deal could eventually be worth £5.1m.
Agency founder and CEO Elizabeth Hindmarch said she accepted the Huntsworth deal because it meant the agency will keep its brand identity and staff structure.
She said: 'I've had suitors over the years but I rejected them as I didn't want to see the agency I had built up swallowed into a large organisation.
This deal ensures we retain our identity.'
The agency, set up in 1982, is 35-strong and ranked 76th in this year's PRWeek Top 150, with fee income of £1.6m.
It was ranked at 100 the previous year.
Clients it brings into the Huntsworth group include Wella, Comet, Nicky Clarke and Miele.
Also this week it was revealed that Huntsworth had expanded its Harrison Cowley operation in Scotland with the acquisition of regionally-based corporate specialist Atlantic PR. This comes just a year after Huntsworth acquired HC, run by CEO and Shandwick founder Lord Chadlington.
The second deal will see the Atlantic team merged into HC's Scottish office to create an 11-strong account-handling team.
This is overseen by Harrison Cowley Scottish director Andrew Jarvie, who will now head a three-strong management team.
Jarvie said: 'There will be a period of change as we are two different groups coming together, we have had a consumer focus and Atlantic has a strong reputation in the corporate area.'
Huntsworth has also confirmed the acquisition of Thomson Financial's investor relations arm Global Consulting Group. Negotiations surrounding the acquisition were revealed by PRWeek last week (PRWeek, 18 October).
Thomson put the business up for sale earlier this year to focus on core financial data and information services.
Commenting on the expansion, Chadlington said: 'Despite adverse market conditions we continue to focus on our core strategy of building a group in our chosen markets which offer growth potential.'