The team announced the move before Saturday's game against Tampa Bay.
Red Sox manager Terry Francona said Jenks felt pain in his left mid-back area while warming up in the bullpen during Friday night's 9-6 loss to the Rays.
Jenks was on the DL from June 8-28 with tightness in the same area. The right-hander, 2-2 in 19 games, will be examined by the team medical staff this weekend in Boston.
"We'll see how concerning it is," Francona said. "There's enough concern that we DL'ed him."
Boston called up left-hander Randy Williams from Triple-A Pawtucket to replace Jenks.
Also, there is no timetable for when Clay Buchholz, sidelined by a strained lower back, will throw off a bullpen mound.
"There is no schedule," Francona said. "It's all how he feels. He need him. We'd love to have him in the short-term, but we really want him in the long-term. So, try to make good judgments."
Buchholz, 6-3 with a 3.48 ERA in 14 starts this season, took Saturday off from throwing after he played catch one day earlier. The right-hander is encouraged by his recent throwing, but still has some discomfort in the back.
"I don't think it's something I can rush," Buchholz said.