Group M will run the account, with the support of MEC. The Dentsu Aegis Network pitch was led by Vizeum, working with group companies.
Starcom MediaVest Group and its sister agency DigitasLBi was also part of the pitch process but dropped out at an earlier stage.
Catherine Kehoe, the managing director for brands and marketing at Lloyds, led the review, which kicked off in October, working with AAR.
The brief covers all Lloyds brands including Lloyds Bank, Halifax, Bank of Scotland and Scottish Widows.
Kehoe said: "Our vision is to be the best bank for customers and our strategic partnership with Group M will help us achieve that.
"Customers have been empowered through access to new sources of information. They expect businesses to understand their individual needs and preferences and expect to be able to access and interact with businesses anytime, anywhere, and on any device.
"The rise of digital technology has disrupted traditional marketing activity. Group M has shown they can play an absolutely critical role in helping us transform our marketing function to respond to these changes, ensuring we better communicate with, and serve, our customers.
"However, Group M consistently demonstrated excellence across all of the capabilities we investigated throughout the pitch process so we’re extremely excited about our new relationship with them."
MEC has held the account since 2009, when it beat ZenithOptimedia to the consolidated account following the merger of Lloyds TSB and HBOS. The agency will be Lloyds’ media agency for a further three years.
Dominic Proctor, the global president at Group M, said: "We recognise the ambition the team have for transforming [Lloyds Banking Group’s] marketing function so have shaped our team, using our best resources and brainpower, to help them on this journey."