Independent financial agency Ptarmigan Media, which has held the account for seven years, repitched for the business against four undisclosed agencies.
Aegon kicked off a media review in October, shortly after appointing Steve Clode as its director of marketing and consumer strategy.
Susan Wilcock, Aegon's head of communications, said Ptarmigan retained the account because of its expertise in financial services.
London-based Ptarmigan, established in 1993, is the largest financial specialist media agency in the UK. According to Nielsen Media Research, it was the largest buyer of investment advertising in 2005.
Ptarmigan handles media for a long list of financial services clients, including Merrill Lynch, Cazenove Fund Management and Blackrock. It won the media account for CMC Markets in June and Investec Asset Management in February.
Ptarmigan has also added specialist direct marketing agency Story to its agency roster after a competitive pitch.