The family of a New Zealand Olympic gold medallist want his stolen medals back.

Thieves took Shane O'Brien's gold medal from the 1984 Los Angeles Olympics when they broke into his family home in Sandringham on Friday night.

O'Brien, Les O'Connell, Conrad Robertson and Keith Trask snatched an unexpected coxless four gold at the 1984 Games, helping secure New Zealand's tally of eight gold medals - the country's best to date.

Along with electrical equipment, jewellery and the gold medal, the thieves also took the rower's bronze and silver medals from the 1986 Commonwealth Games in Edinburgh.

The rower's brother, Gary, said the Commonwealth medals held the most sentimental value as their mother, Audrey, had a brain haemorrhage on the eve of the Games.

Gary O'Brien remembers parting ways with his brother at Heathrow Airport. He flew home to New Zealand to be with his mother while Shane went on to compete in Edinburgh.

"He was rowing over there while mum was fighting for her life."

Mrs O'Brien, 76, who lives alone in the family home, was at Gary O'Brien's for a couple of days when burglars pounced. Neighbours saw curtains drawn and lights on inside the house at 11pm Friday.

Gary O'Brien estimates $5000 worth of items were taken, but the medals were beyond monetary value.

Gary O'Brien said his brother, who has lived in Britain for the past 16 years, was contemplating coming back to help sort out matters, but their mother was bearing the brunt of the burglary.

He was not sure whether she would return to her home of 50 years.

"We're a bit fearful of her returning to the house ... These people are essentially forcing us to change her lifestyle.

"She can't drive because of the brain haemorrhage, and one of the issues that we're having to consider is what her future's going to be."

But most importantly, he said, the family wanted the medals back.