The partnership will see CHI acquire a 50.1 per cent stake in Halpern, with 49.9 per cent retained by agency founder Jenny Halpern Prince and Halpern senior management. The Halpern team will work alongside CHI & Partners founder Johnny Hornby and retain managerial control.
CHI is part of the WPP group and covers advertising, digital, creative, content, media buying and direct marketing.
The acquisition of Halpern will see CHI's offering include PR for the first time.
Halpern founder Jenny Halpern Prince said: "The partnership with CHI provides us with the perfect opportunity to work with Johnny and his inspiring team and clients. It strengthens our offering in both the UK, and worldwide, which will help grow the Halpern business substantially in the coming years."
Halpern managing director Jen Burner added the agency was hoping to benefit from the pool of talent offered by CHI. She said there are plans to expand the agency's capabilities to outside the UK soon.
The deal is effective today and Halpern’s London offices will move to the CHI & Partners in early 2014 with further global bases under review.