The credit-card company previously used VCCP to produce its online advertising, but the agency resigned the account due to a conflict with O2, which launched a debit card in the middle of last year.
The successful shop will take on all of Capital One's digital strategy and advertising, which now represents a significant proportion of its marketing activity.
In January 2009, Capital One shifted the majority of its marketing budget out of direct mail and into online media.
Before it changed its focus to online, the financial services company was spending around £2 million on digital advertising, according to 2008 Nielsen Media figures.
Since then, social networking sites have become a major source of internet traffic for Capital One. Last year, Facebook was its second-biggest traffic source after Google.
The pitch does not include Capital One's creative account, which remains with Abbott Mead Vickers BBDO, while MediaVest will continue to handle its digital media planning and buying.