Valdes replaces catcher Erik Kratz, whom the Phillies optioned to Lehigh Valley on Tuesday.
Valdes went 2-0 with a 2.13 ERA in 11 appearances in his first stint with the Phillies this season. The Phillies optioned him to Triple-A on June 8 when they promoted rookie right-hander B.J. Rosenberg because right-handers Chad Qualls and Michael Schwimer were struggling.
Valdes has 62 big league appearances over three seasons with the Mets, Cardinals, Yankees and Phillies, making him the fourth-most experienced reliever in the bullpen behind Qualls (567 appearances), Jonathan Papelbon (423) and Antonio Bastardo (121).
Schwimer (24), Joe Savery (20) and Jake Diekman (13) are rookies.
"We could use a veteran arm," Phillies manager Charlie Manuel said. "The guys we've got, they're definitely going to be good pitchers. They've got talent. There's going to be some growing pains. There's going to be some inconsistencies. That's kind of natural until they get to the place where they can have command and use the outer- and inner-half of the plate."
Manuel said he believes Valdes can give the Phillies multiple innings and also pitch in high-leverage situations.
"When we sent him down, we didn't plan on him staying there very long," Manuel said.