[5] In 1979, at the age of 26, Bradley founded the Research Council of Washington, later renamed The Advisory Board Company.

[7] Both companies became publicly traded, with the Advisory Board on NASDAQ and CEB on NYSE, and later acquired by Optum and Gartner, respectively.

He hired Michael Kelly, a well-known journalist who had just been fired from The New Republic after frequently clashing with owner Martin Peretz.

In 1999, Bradley purchased The Atlantic from publisher and real estate tycoon Mort Zuckerman for $10 million.

Bradley doubled the newsroom budget of The Atlantic, allowing the magazine to embark on a hiring spree, offering contracts to 25 new writers.

[9] In 2012, Bradley launched Quartz, a business-news publication aimed at mobile-device users; he sold it in 2018 to Uzabase, a Japanese media company, for between $75 and $110 million.

In 2011, Bradley led a team of researchers and journalists looking for freelance reporter Clare Gillis, who had been captured by Libyan soldiers loyal to Muammar Qaddafi.

Larry Wright wrote an article[10] about a dinner at Bradley's house during which the families of five of the missing hostages met for the first time.

To avoid a conflict of interest, Bradley directed Wright to publish the story in The Atlantic's competitor, The New Yorker.

[11] On 28 July 2017, Bradley sold his majority ownership of The Atlantic to the Emerson Collective, which is an organization owned by multi-billionaire investor and philanthropist Laurene Powell Jobs.

He founded the Child Protection Network,[13] the largest system of acute care facilities for abused children in the Philippines.