Guardado, who pitched for Minnesota from 1993-2003, was 3-3 with four saves and a 3.65 ERA for Texas this season. The left-hander has allowed 38 hits, walked 17 and struck out 28 in 49 1/3 innings.
He became known as "Everyday Eddie" for his seemingly ability to pitch every day -- he pitched in at least 63 games each year in his last eight seasons in Minnesota.
The deal was first reported by the Dallas Morning News.
Guardado has 187 career saves, 116 with Minnesota, where he played from 1993-03 and earned his nickname for the number of innings he logged. He'll help in the eighth inning, a problem for the Twins this season after setup man Pat Neshek hurt his elbow and landed on the disabled list.
Minnesota blew a 3-2 lead in the eighth and lost 5-3 on Sunday to the Angels.
The Twins planned a roster move for later Monday, before their game at Seattle.
Texas general manager Jon Daniels said he wouldn't have made the move if the Rangers were still in the playoff race. Minnesota claimed Guardado when he was placed on waivers.
"He was very complimentary of the situation of the organization and appreciated the opportunity to go back to the Twins," Daniels said in a conference call. "Certainly only positive feelings on both sides.
"If we were three games out, we wouldn't be in a position to be trading veterans," he added. "We'd probably be on the other side of it, looking to add."
To take Guardado's place, the Rangers purchased the contract of left-hander Bill White from Triple-A Oklahoma. White was expected to join the team and be available in the bullpen for Monday's game at Kansas City.
Right-hander Frank Francisco was expected to move into the ninth-inning role.
"It sounds like Frankie's going to get the first shot at it," Daniels said, declining to speculate on the competition for the closer job next season. "Let's see how the next five weeks go. I'd like to see Frankie step up and perform in that role and handle it."
Minnesota sent 21-year-old right-hander Mark Hamburger to the Rangers, who will assign him to their Class-A club in Clinton, Iowa. Hamburger, a Mounds View (Minn.) High School grad, was signed by the Twins after a local tryout camp. He was the Appalachian League's Closer of the Year for rookie-level Elizabethton.
Texas also recalled outfielder Nelson Cruz from Triple-A Oklahoma and designated outfielder Jason Ellison for assignment. Cruz, who spent parts of the past two seasons with the Rangers but hasn't played in the majors this year, hit .342 with 37 home runs and 99 RBIs in 103 games for Oklahoma.
"He's got his confidence back, and we're just going to put him in there and let him swing and see how it goes," Daniels said.