The 23-year-old, who has played 17 Test matches for Australia, said the move was a new beginning after being discarded from the national side.
"The next two years are the most critical in my cricket career and I'm not going to leave any stone unturned to make sure I put myself back into contention to play again for Australia," Hughes said in a statement on Thursday.
Hughes was overlooked for a Cricket Australia contract but believed his omission was "not the end of the world".
"In fact, in lots of ways, it's a new beginning," he said.
Hughes, playing in England with Worcestershire, has played 71 first-class matches, and averages 46.52 with the bat including 17 centuries.