MediaCom successfully fought off Aegis's Carat and fellow Group M shop MEC for the insurance giant, which includes the brands Direct Line, Privilege, Green Flag and Churchill.
Direct Line Group spent £86 million on media in 2012, according to Nielsen.
The group marketing director Mark Evans ran the review, which began in March. His arrival at the insurance giant last year, as well as the company's aim to slash costs by £100 million by 2014, triggered the process.
DLG was previously part of the Royal Bank of Scotland, but was spun out of the bank in an IPO in October as part of the conditions of RBS’s 2008 taxpayer-funded bailout. RBS still has a minority stake in the company.
MediaCom defended the business in an RBS media review in 2011, despite losing the NatWest and RBS retail accounts to ZenithOptimedia.
Mark Evans said, "We constantly review our media strategy to ensure it is appropriate for the needs of our business. Following a pitch review process involving several different agencies, we have re-appointed Mediacom as our media partner, as we felt their proposal best met the strategic vision for our media activity.
"It’s great to be able to continue our relationship and together we will work to deliver the next exciting stage in the future of Direct Line Group."