The deal was apparently closed on Monday and will see the 19-year-old star playing Nike balls, and wearing Nike shoes and gloves.
Baddeley is now part of a growing regime of top golfers, including World No. 1 Tiger Woods and David Duval, who have signed deals with the sporting industry giant.
Baddeley is coming off his first season as a professional, in which he won the Order of Merit title for the ANZ Tour, collecting wins at the Australian Open and the Greg Norman Holden International. He became only the second rookie ever to do so.
Details of the contract with Nike have not been released.
Click here for more news headlines!