The 36-year-old right-hander had a bounce-back year after signing with the Atlanta Braves before last season, finishing 12-12 with a 3.57 ERA in 33 starts. He pitched 204 1/3 innings, the first time he surpassed 200 innings since 2007, when he was with the Cincinnati Reds.
"Aaron brings a wealth of experience and durability to our rotation," Phillies general manager Ruben Amaro Jr. said in a statement. "He had a very solid season for the Braves last year and will complement the left-handers in our rotation nicely."
In 13 seasons with the Oakland Athletics, Reds, San Diego Padres, Los Angeles Dodgers, Seattle Mariners, New York Mets and Braves, Harang is 122-128 with a 4.21 ERA. In 2007, he finished fourth in National League Cy Young voting after going 16-6 with a 3.73 ERA in 34 starts.
He was paid $1 million in 2014.