Redmond has spent the past four seasons in Triple-A Gwinnett, seeing action in 101 games.
The 27-year-old righty has made 18 starts in 2012, with a 6-6 record, 3.58 ERA and one shutout.
In 199 career Minor League appearances, including 193 starts, Redmond is 69-56 with a 3.57 ERA, four complete games and three shutouts.
He will be assigned to the starting rotation for Triple-A Louisville, according to Reds president of baseball operations and general manager Walt Jocketty.
"He's a guy who pitches a lot of innings; he's a big, strong, durable guy," Jocketty said. "He has an above-average fastball and good command, and he's a guy that we think will definitely help us in an emergency situation as a starter, but he may pitch out of the bullpen for us, too."
Janish, 29, was drafted by the Reds in 2004 and spent time in the big leagues from 08-11, but has been in Louisville the entire '12 season, where he hit .237 with four homers and 11 RBIs in 49 games.
With highly touted infield prospects Billy Hamilton and Didi Gregorius making their mark in the Minors, Jocketty said Atlanta would be a better fit for Janish.
"The Braves obviously had some injuries and were looking for middle-infield help, and they contacted us about Janish," Jocketty said. "We had been trying to get Paul an opportunity to get back to the Major Leagues. We felt he deserved to play in the Major Leagues, and the opportunity wasn't going to be here for a while. This really works well for Paul."