A company-wide team from Golin/Harris participated in the pitch, and multiple offices will handle the £1.9m brief, including New York, Chicago, San Francisco, and Los Angeles.
Visa's search began in the spring, with Golin/Harris, Ketchum and several other contenders.
The process took several months because of 'a very strong pool of candidates', said Visa USA executive vice -president of corporate relations Barie Carmichael: 'We took our time to select the one that was the best match for us.'
'Comms is vitally important to Visa USA,' she added, pointing out that CEO Carl Pascarella and other executives were also part of the decision-making team.
The focus will be on developing a 'greater share of the way people pay for things' said Carmichael: 'Visa is a payments leader and our major competitors are cash and cheques.
'This is a highly competitive environment - we want to be the best way to pay and to be paid. My mission is to advance that goal through the value-add of comms,' she added.
Golin/Harris president Fred Cook said the work will entail a broad scope, including further establishing Visa USA as a thought leader, developing its brand and addressing payment-industry issues.
Visa USA has worked with Ketchum for the past six years.
Ketchum CEO Ray Kotcher said: 'Obviously, this isn't what we wanted to hear, but we were planning for something like this happening.
'We didn't have (Visa USA) factored into our 2003 plan, so the impact should be quite minimal,' he added.
Golin/Harris's appointment does not affect Visa International's retained agency relationship with the GCI Group.