Hamilton, who's been on the disabled list since July 12 with a sprained right wrist, was returned from a rehabiliation assignment at Triple-A Louisville and reinstated from the 15-day disabled list.
To make room on the roster, infielder Mark Bellhorn was designated for assignment. Bellhorn made just five appearances for the Reds as a pinch-hitter and one as a defensive replacement.
Hamilton was pulled from Saturday's game at Louisville after going 0-for-2 with a walk and run scored. He was in the locker room when Bats manager Rick Sweet told him to pack his bags for Cincinnati.
"He told me, 'You're going back,'" Hamilton said. "All the coaches filed in to say good-bye. I'd rather not be down there, but it was fun. They're all good people."
Hamilton hit .375 with two RBIs in five rehab appearances at Louisville.
He arrived in Cincinnati around 1:30 a.m. ET on Sunday.
Hamilton was not in Sunday's starting lineup but said he had been hoping for a start.
"Absolutely," he said. "Put me in coach. I'm ready to go, 100 percent. I want to stay healthy and play."
Hamilton earned National League Rookie of the Month honors in April. He is batting .279 with 14 home runs and 30 RBIs in 64 games. He received 151,245 All-Star write-in votes.
This was his second stint this season on the disabled list. He also was on the DL from May 22 to June 3 with a gastrointestinal infection.
"It's been a pretty good season," he said. "If I hadn't gotten sick the first time, I would've played in 100 games by now instead of 60-some. I'm hoping to get 150 to 200 more at-bats."
Sunday is "Faith Day" at Great American Ball Park with a postgame concert by Christian rock band MercyMe. Hamilton, who is a participant in the day's festivities, feels fortunate to return to the club in time for the event.
"That's God's timing," he said. "Could've happened any time. Just so happened on the right day."
Hamilton, a former No. 1 overall Draft choice of the Devil Rays, made the Reds' roster out of Spring Training after being out of the game for nearly four years following a lengthy bout with alcohol and drug abuse.
"The stuff that happens in life, job-wise, is so not even close to what I went through," he said. "I have faith that God will pull me through whatever it is. A wrist injury isn't that big of a deal."
Homer update: Rookie right-hander Homer Bailey strolled through the clubhouse Sunday morning drenched in sweat after a 40-pitch session off the bullpen mound.
"It was the first time I've thrown breaking balls," Bailey said. "It's been long enough. I didn't feel a thing today. Just trying to get back into it."
Bailey, who's on the disabled list with a groin injury, is heading to Sarasota, Fla., to begin a throwing program. There is no timetable for his return.
Bailey, the Reds' top Draft choice in 2004, made his much-anticipated Major League debut this season. He was sent to Triple-A Louisville in order to keep him on a regular pitching schedule through the All-Star break before landing on the DL.
"It's been one helluva year," Bailey said.
Day of rest: Ken Griffey Jr. and Alex Gonzalez were not in the starting lineup on Sunday. Reds manager Pete Mackanin said Griffey, with an off-day Monday in Chicago, is being given what amounts to two days off. Gonzalez is nursing a tender throwing elbow. The moves also allowed Mackanin to keep Jeff Keppinger's bat in the lineup. Keppinger is batting .354. He's hit safely in six of his last seven games. He went 2-for-4 with three RBIs in Saturday's victory.
Fundraising success: Through two "Mystery Ball" sales, the Reds' wives raised $27,890 to benefit Camp Erin-Cincinnati, a free bereavement camp for children ages 6-17 who have experienced the death of a loved one. Camp Erin-Cincinnati is scheduled to open next summer. The free camps are created by the Moyer Foundation, founded in 2000 by Phillies pitcher Jamie Moyer and his wife, Karen. They've raised more than $10 million to help children in severe stress and already have established Camp Erin programs in eight cities. Their goal is to establish 50 camps by 2010, including a camp in each big league city.
Farm report: Joey Votto went 2-for-5 with a double and three RBIs in Triple-A Louisville's 7-5 victory over Norfolk. ... Third baseman Enrique Cruz extended his hitting streak to 10 games in Double-A Chattanooga's 5-3 loss at Montgomery. ... Todd Frazier, who had a career-high four hits Friday night, collected three hits, including a double and triple, in Rookie League Billings' 9-2 victory over Idaho Falls on Saturday.
Coming up: The Reds will travel to Chicago on Monday. They begin a three-game series against the Cubs at Wrigley Field at 8:05 p.m. ET Tuesday, with Reds right-hander Aaron Harang (11-3, 3.37 ERA) being opposed by Cubs right-hander Carlos Zambrano (14-8, 3.69 ERA). p>
Jeff Wallner is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.