The Edinburgh-based agency, part of the Aegis network, has been appointed on a one-year contract, commencing in January, but could potentially handle media beyond the next 12 months.
The tourist commission has earmarked £2.4m to be spent each year over a minimum of the next three years.
The appointment marks California's first major UK advertising campaign, spanning television, press and online in conjunction with promotional partnership activity.
California governor Arnold Schwarzenegger is supporting the drive to increase visitor numbers after a fall in tourism in the aftermath of the terrorist attacks on 11 September, 2001.
The media review was run by the California tourism body's UK marketing and TV production agency, Black Diamond. The agency provides marketing, travel trade and public relations representation as California Tourism UK & Ireland from its headquarters in Covent Garden.
It will undertake all local creative and production duties on the account.