The 22-year-old completed his medical examination on Thursday morning and will initally join on loan, although his contract also stipulates that Freiburg have an option to make the move permanent.
Mehmedi made 84 appearances for FC Zurich between 2007 and 2011, scoring 19 times. In 2011 the front man earned his first international cap for Switzerland before agreeing a move to Dynamo Kiev in January 2012.
"We've been in touch with Admir Mehmedi for many years," said Freiburg's acting sporting director Klemens Hartenbach. "We're delighted the transfer went through. He's a very versatile attacking player who understands the game. He's already proven that he can play at the highest level."