Stewart Ginn was born in Melbourne and grew up behind the twelfth green of the Royal Melbourne Golf Club where he started caddying at the age of ten.
In the 1970s and 1980s, he won several professional tournaments on the PGA Tour of Australasia and one on the European Tour, the 1974 Martini International. He also played regularly on the Asia Golf Circuit, winning three tournaments, and on the Japan Golf Tour, where he has one win. He won the inaugural PGA Tour of Australia Order of Merit in 1973.
His win at the 1979 New Zealand Open was played at St.Clair Golf Club, Dunedin on 6th to the 9th of December. In wild weather, the tournament opening round produced a remarkable 63 from Ball the Australian who had fallen at the final hurdle a year previously.
When the weather switched to bitterly cold the next day, his 78 saw him five strokes off the pace set by Simon Owen from Ginn, Charles, Davis and Barnes. Round three was played in fine but very cold conditions and Owen with a poor start recovered to maintain his two-stroke advantage over Ginn, with Barnes two further back.
With disappointing final rounds were returned by Owen 74, Coombes 77 and Charles 79, it was Ginn who continued his run of scores that did not exceed the par of 71 and which was sufficient for him to gain the 1979 New Zealand Open.
As a senior, he played full-time on the U.S.-based Champions Tour from 2000 to 2004. His one official money win at that level came at one of the senior majors, the 2002 Senior Players Championship.