Worley will be making his debut with the Pirates, who acquired him on March 25 from the Minnesota Twins for cash considerations.
He is 19-18 with a 4.05 ERA while pitching parts of three seasons with the Philadelphia Phillies and last year with the Twins.
Pirates manager Clint Hurdle said Worley, who was just 1-5 with a 7.21 ERA last season with the Twins, is a pitcher he has liked for years.
"Fastball command, a changeup that has been a go-to pitch, and he can spin the ball on occasion," Hurdle said of Worley, who was 3-2 with a 4.30 ERA at Indianapolis this season. "The past three or four games he pitched in the minor leagues have been crisp."
The Pirates are expected to make another roster move Sunday to clear space for Worley.