The deal involves the reported acquisition of an 82.8 per cent stake in We Are Social, which will become BlueFocus’ primary digital agency brand outside China.
The move by BlueFocus, which is listed on the Shenzhen stock exchange with a market cap of $3.7bn (£2.27bn), follows the company buying up a stake in Huntsworth earlier this year.
It is subject to Chinese regulatory approval, expected to be received within three months, with We Are Social advised by Results International and Osborne Clarke, and BlueFocus by BDO and Ashurst.
Both parties are understood to have been in discussions since February.
We Are Social, which shares electronics company Lenovo as a major client with BlueFocus, was launched in 2008 by Robin Grant and Nathan McDonald.
It now employs 400 people across its eight global offices in New York, London, Paris, Milan, Munich, Singapore, Sydney and São Paulo.
Robin Grant, co-founder of We Are Social, said: "We Are Social has now been running for about five years and we knew that if we wanted to achieve our ambitions we really needed to find the right partner to move the business forward.
"As we looked at all the options, Blue Focus became the obvious choice due to the scale of the ambitions and a shared empathy between the two companies and for our clients there is a huge bonus of being given unparalleled insight into the Chinese market, which is invaluable.
"We want to accelerate our mission to put social media at the centre of marketing."
BlueFocus acquired a 19.8 per cent stake in Huntsworth worth £36.5m in April, with Huntsworth CEO Lord Chadlington explaining the move would help reduce the Group's debt.