Ginsberg began his legal career as an attorney at Simpson Thacher & Bartlett. After that he served in the Clinton Administration at the White House’s Counsel office and the U.S. Department of Justice. In 1995, Ginsberg became Senior Editor and legal counsel of George, the magazine started by John F. Kennedy, Jr. Ginsberg spent eleven years at News Corporation, serving in several senior roles, including most recently as Executive Vice President of Global Marketing and Corporate Affairs. During this tenure, Ginsberg was a close confidant of Rupert Murdoch and Peter Chernin. In 2009, Ginsberg stepped down from his role at News Corp. following the departure of Chernin, who for years served as Murdoch’s top lieutenant. Ginsberg had been close to Chernin and was also closely associated with Democratic politics. Ginsberg was credited with brokering numerous relationships between Murdoch and prominent Democratic politicians. He arranged lunches with Bill Clinton and orchestrated a fundraiser for Hillary Clinton in 2006. Ginsberg also arranged a meeting between Murdoch and Barack Obama in 2008. Ginsberg was described as the “Murdoch Interpreter - the point man for all of the information going out of the company, as weell as the information going into the company.” He was also "a point man for News Corp.’s 2007 purchase of Dow Jones, publisher of The Wall Street Journal." Ginsberg joined Time Warner in February 2010. His new job was described "as a senior adviser to its CEOJeff Bewkes..., executive vice president,... responsible for a range of corporate issues, including communications and marketing, and for evangelism across the media industry for Mr. Bewkes’s initiatives.” Ginsberg again served as “the connection to Washington on multiple instances.” The Wall Street Journal reported in early 2017 that Ginsberg met with Jared Kushner at the White House. At the meeting Kushner “expressed the administration's deep concerns about CNN’s according to an administration official. Ginsberg held a breakfast meeting in 2016 with his former colleague Peter Cherning in Martha’s Vineyard where Cherning first broached the possibility of AT&T acquiring Time Warner. Ginsberg was “in the middle of the fight to defend the company’s sale to AT&T.” Two years later the deal was completed and Ginsberg left the company along with other senior colleagues from Time Warner. In October 2018 Ginsberg was hired by Softbank as the company's Global Chief of Communications.