Neiwand was born in Melbourne, Victoria, on 4 September 1966, the son of Ronald Charles Neiwand.
Neiwand represented his country at cycling for more than a decade. He was Commonwealth Games sprint champion in 1986 and won his first Olympic medal at the 1988 Summer Olympics in Seoul, winning bronze in the sprint event.
He repeated his success at the Commonwealth Games in 1990, taking the gold in the sprint. Neiwand won his first World Championship medal in 1991 in Stuttgart, winning the bronze in the sprint. He then went on to become the World Champion in both the keirin and sprint in 1993. 1994 saw Neiwand complete a hat-trick, winning his successive third sprint gold medal at the Commonwealth Games.
Neiwand spiralled into depression after missing his goal of a gold medal in the Keirin at the 2000 Summer Olympics. He began drinking heavily, his marriage fell apart and he gained weight, ballooning to 116 kg.
In 2006 Neiwand was sentenced to eighteen months in prison for breaching a court order preventing him from harassing a former girlfriend.
Neiwand began his sentence at Port Phillip before being moved to Beechworth. He was released on probation after serving nine months in jail. He has since rebuilt his relationship with his children, Malcolm and Courtney, and ex-wife, Cathy.
Neiwand joined the Sunrise Foundation in 2007, an organisation which, through the high schools, aims to demystify and tackle depression in the community. It is run by former North Melbourne and Sydney footballer, Wayne Schwass.
On 5 December 2011 Niewand pleaded guilty to two charges of wilful and obscene exposure in Melbourne, after having been charged on two separate occasions in January and May 2011 for exposing himself to women while masturbating in his car. These offences occurred after Niewand had been released on a court order in December 2010 on unrelated charges, where he had been ordered to attend Forensicare and counselling about his behaviour. The court heard that having attended counselling over the previous six months Niewand had made significant progress, had his drinking problems under control, and was concerned and upset about his offending and his predicament. The magistrate regarded a report from the Forensicare counsellor as "promising", adjourning the case until March 2012 when he was sentenced to four months jail, wholly suspended for two years.
Neiwand received the Australian Sports Medal on 14 July 2000 and the Centenary Medal on 1 January 2001.