Dell called the pitch in September, with Omnicom pitting OMD against Carat in the UK, and PHD against Carat in other European markets.
Carat holds the £33 million offline and £11 million online media accounts in the UK. The business has been with the Aegis-owned agency for the past 17 years, with Carat handling the UK and small business account since 1989.
Currently, Dell is struggling under pressure from its rivals. Net income for the second quarter was $502 million, compared with $1.02 billion for the same period last year.
Dell is already Carat's biggest-spending online client across Europe, and the win comes on the heels of Carat landing the General Motors and Alliance & Leicester media accounts.
In September, Alliance & Leicester consolidated its £30 million UK media account into Carat, while GM moved its £400 million European account into the network. Last week, the wins carried on coming, with Wal-Mart handing its US business to Carat.
Carat and Dell refused to comment on the news.