The deal is a major league contract for $1.1 million guaranteed, a baseball source told ESPN.com senior writer Jerry Crasnick, and includes $350,000 in incentives.
The 35-year-old right-hander went 4-1 with one save and a 3.14 ERA in 76 appearances for the Atlanta Braves last season.
To make room on the 40-man roster, the Phillies designated righty J.C. Ramirez for assignment.
From 2008 to 2010 with Philadelphia, Durbin went 11-7 with a 3.62 ERA in 194 appearances.
The Phillies on Monday also agreed to a minor league contract with infielder Yuniesky Betancourt, who was given an invitation to major league spring training.
The 30-year-old Betancourt hit .228 with 14 doubles, seven home runs and 36 RBIs in 57 games with Kansas City last season. He played 46 games at second base, eight at third base and one at shortstop.
Information from The Associated Press was used in this report.