He turned professional in 1979 and has extensive experience on the Professional Golf Association Tour of Australasia and the European Tour. The following year he was runner-up to fellow Australian Ian Baker-Finch at the Open Championship at Royal Birkdale. In his prime he played occasionally in the United States, but he never had a top ten finish in any Professional Golf Association Tour event other than the Open Championship.
His round of 61 at the Australian Professional Golf Association Championship at Concord in 1992 was his best professional score recorded.
Harwood continues to play on the Tour. He again finished in the top-10 in the Order of Merit in 2011.
European Tour (5) 1988 Portuguese Open Professional Golf Association Tour of Australasia (2) Other wins (5) European Seniors Tour wins (1) Other senior wins (17).
1988 Portuguese Open 1989 Product Lifecycle Management Open 1990 Volvo Professional Golf Association Championship, Volvo Masters 1991 Georgia European Open 1986 Australian Professional Golf Association Championship 1990 West End South Australian Open 1984 Fijian Open, Pacific Harbour Open (Fiji), Western Samoan Open 1986 Naturgas Open (Sweden) 1996 Victorian Professional Golf Association Championship 2009 OKI Castellon Senior Tour Championship 2009 Australian Open Championship, Tasmanian Senior Open, NSW Professional Golf Association Championship 2010 New Zealand Handa Professional Golf Association Championship, Tasmanian Senior Open, Queensland Professional Golf Association Senior Championship 2011 City of South Perth Masters Pro Am (Asia Pacific Champions Tour), NSW Professional Golf Association Championship 2012 Australian Professional Golf Association Championship, Tasmanian Senior Open, Sri Lankan Airlines Senior Golf Masters 2013 Victorian Senior Open 2015 Tasmanian Senior Open, Société Anonyme Professional Golf Association Senior Championship, Fijian Senior Open, NSW Professional Golf Association Championship 2016 Tasmanian Senior Open.
Prior to joining the European Seniors Tour, Harwood served as a board member of the Australian Professional Golf Association in the early 2000s.