Klemm has been executive director of the MLB Umpire Camps since January 2008. He was an umpire in the minor leagues for nine seasons and also worked part-time in the Major Leagues.
Klemm is to work out of the MLB Advanced Media headquarters in New York, the command post for the new replay system.
"Major League Baseball is pleased to welcome Justin Klemm as director of replay," MLB Senior Vice President of Baseball Operations Peter Woodfork said Thursday in a release. "As we move forward with our new system, Justin's background and experiences on and off the field will be vital resources to not only our umpires, but many of us as at the Commissioner's Office and MLB Advanced Media."
MLB also announced the hiring of seven new full-time umpires.
The organization needed to add six umpires to handle replay assignments. The seventh vacancy was created by the death of 21-season umpire Wally Bell last October.
Baseball is expanding replay beginning this season to allow for appeals of calls such as fair-foul, fan interference, trap plays in the outfield and hit by pitch. Calls of balls and strikes, on-field interference and obstruction aren't reviewable.