At Triple-A Iowa, he batted .337 in 23 games with six home runs, two doubles, two triples and 16 RBIs.
"It might have been a positive for me to go to Triple-A and play every day and get my confidence back," Sweeney said.
The Cubs promoted Sweeney and pitcher Rafael Dolis from Triple-A Iowa on Monday, and optioned outfielder Dave Sappelt to the Minor League team. Reliever Kameron Loe was designated for assignment to make room on the 40-man roster for Sweeney.
Sweeney was pulled from the second game of Iowa's Sunday doubleheader and told by manager Marty Pevey that he was headed to the big leagues. He was considering at least three teams, and after talking to Theo Epstein, Cubs president of baseball operations, decided Chicago was a good fit.
A left-handed hitter, Sweeney, 28, has played for the White Sox, Athletics and Red Sox, and has a career .280 batting average over seven seasons in the big leagues.
Sappelt, 26, was used in Cubs manager Dale Sveum's platoon against left-handed pitchers. In 20 games with the Cubs, Sappelt was batting .178 (8-for-45).
The Cubs had claimed Loe, 31, off waivers from the Mariners on April 14. On Sunday, he gave up one run on one hit and two walks in one inning against the Reds, and has a 5.40 ERA in seven games.
"We want him to go to Triple-A to get things worked out," Sveum said of Loe. "He's a nice piece to have when that sinker is working correctly. He just needs to iron out some mechanics."
Dolis, 25, appeared in 34 games last year with the Cubs. In eight games with Iowa, the right-hander has given up three runs on six hits and three walks over 7 2/3 innings, striking out seven.
Sweeney did admit it was tough to go back to the Minor Leagues after spending so much time in the big leagues.
"I could go down and be [ticked] off or I could go down and show them I was healthy and still hit and try to get back up as soon as I could," he said.
Perhaps the best part about the timing of the callup is that his parents had traveled from Cedar Rapids, Iowa, and were in Des Moines to watch Sweeney play.
"My brother is in the Midwest League, and they had gone to see him a bunch," Sweeney said. "I felt like a little kid again. I'd never gotten called up in the middle of the year. It was definitely different being pulled out of a game to get called up."