Teneo, which is headquartered in New York, also acquired Blue Rubicon and StockWell in July, making financial and corporate comms agency Pendomer its third UK acquisition.
Pendomer was founded in 2012 by Charles Armitstead and Ben Foster, former managing directors at what is now FTI Consulting. Clients include Virgin Active, Pizza Express and Heineken, the latter since 2013.
Pendomer employs seven people, meaning that Teneo will have more than 200 professionals in London. It will initially retain its own brand before being integrated "in due course", a spokeswoman for Teneo said. Its leadership will report to Teneo International chairman Charles Watson.
Terms of the transaction were not disclosed.
Declan Kelly, chair and CEO of Teneo, said: "We have known the team at Pendomer for many years and respect the way that they have built a successful, highly profitable business from a standing start. Their entrepreneurialism, innovative approach and hugely respected advisory capabilities will help to significantly accelerate our ambition to expand rapidly in the UK and across Europe."
Armitstead, managing partner of Pendomer, said the deal was "an incredibly exciting opportunity for us and for our clients", adding: "We look forward to contributing to Teneo's success and helping to take the business forward."