Atos will start providing TfL's service desk for up to 25,000 users across multiple locations for up to four years from March.
The firm will be responsible for logging, tracking and managing requests via phone, e-mail, web portal and instant messaging using TfL's Remedy IT Service Management (ITSM) tool.
It will also provide e-mail authentication and configuration, printing, remote access and complaints handling.
The contract is part of TfL's wider move to a 'Towers' model of disaggregated, individual contracts for specific technology services such as desktops, telephony and hosting, rather than using a single vendor for all of its IT.
Atos has promised its service desk will gather real-time information across the organisation to identify trends and identify issues across the different 'Towers'. The firm added it will "drive service improvements, cost efficiencies and deliver innovations in service to end users".
CSC was the previous provider for TfL's service desk, as part of a wider outsourcing arrangement agreed in 2007 and extended at a cost of £21 million in 2012.
TfL's chief information officer Steve Townsend said: "Transport for London promised we were going to transform the way we provide our information management services to our business and ultimately our customers.
"Atos provided a compelling bid and their approach complemented our transformation plan, making them the ideal partner to help take our plans forward."
TfL launched a contactless payments service at the end of last year so passengers can now pay for journeys using their bank cards or devices.
Visa UK managing director Kevin Jenkins recently predicted 100 million journeys will be paid for using contactless technology this year. He said debit and credit cards will eventually account for 95 percent of all transactions in the UK within 10 years.
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