The Boston-based agency won the account after a four-way pitch against Euro RSCG in New York, McKinney in Durham, North Carolina and GSD&M in Austin, Texas. Doner in Southfield Michigan, the incumbent, resigned the business at the start of the review.
Progressive Direct is the third-largest seller of car insurance in the US after Geico and Allstate. The company is worth more than $4 billion.
Pam Hamlin (pictured), the president of Arnold, said: "It is a unique and innovative company and we're eager to begin working with it."