The London team will be headed by planning and consultancy director Ian Dawson, who was appointed in November.
The move represents Equi=Media setting out its stall as an independent, UK-owned search specialist, and will ease the company's planned expansion into Europe. The search market is consolidating, for example, with Spannerworks selling out to US company iCrossing in February this year.
Andrew Burgess, managing director of Equi=Media, said the company would retain its head office in Swindon, but this would be boosted by the team in London.
Burgess said: "The challenge for us as a business is that it's a low cost base in Swindon, but we were sending 10 to 15 people up to London every week."
The remit of the new office in Baker Street - which is scheduled to open after Easter - is to build on Equi=Media's relationships with clients and agencies.
The company has also beefed up its management team, including doubling the size of its board of directors from three to six in the past year.
Burgess said he had no intention of selling the firm, but would form partnerships where it would benefit the company, staff and clients.
Equi=Media has had a strategic partnership with media agency John Ayling & Associates since July last year.