The Cubs will be receiving Ben Brown, a pitching prospect, in return for the trade, Phillies President of Baseball Operations David Dombrowski announced today.
With the Cubs well out of playoff contention and the 37-year-old Robertson eligible for free agency after this season, the reliever was widely expected to be dealt before Tuesday's 6 p.m. ET trade deadline. He had been linked to several teams, including the Toronto Blue Jays.
Robertson returned from Tommy John surgery late last season with the Tampa Bay Rays after winning a silver medal with the United States at the Tokyo Olympics.
He signed a one-year contract with the Cubs prior to this season and has been effective, going 3-0 with a 2.23 ERA, 14 saves, 51 strikeouts and 19 walks.
Robertson also has played for the New York Yankees, Chicago White Sox and Philadelphia Phillies since breaking into the majors in the Bronx in 2008. He won a World Series with the Yankees in 2009 and was an All-Star with New York in 2011.