The consolidation, which follows a rebranding of Agency.com's US Itraffic offices in June, will ditch the Itraffic brand.
The unified company will operate out of Agency.com's offices under the single brand name. It will be divided into two divisions; web development and online marketing.
David Eastman, the former head of Agency.com Amsterdam, who was recently appointed to the role of managing director of Agency.com London, will continue to head the merged agency.
Eastman replaced the former managing director, Andy Hobsbawm, who was drafted in to hold the fort at Itraffic following an exodus of key management figures.
Itraffic UK's managing director, Jon Sharpe, the sales and marketing director, Ethan Seal and Matt Gorzkowski, Itraffic's client services director, quit in August to set up their own outfit, which is operating out of M&C Saatchi's offices.
Agency.com is now launching a hunt for two new managing directors. In the interim, Hobsbawm will head the online advertising side. The agency is searching internally and externally for a head of web development.
Itraffic was founded in 1995 and was acquired by Agency.com in 1999.
Its main clients include Heineken UK, Sears, Wells Fargo and British Airways.
Wanadoo, an Itraffic client, recently launched a hunt for a new agency.
The process is being overseen by the AAR.