The five robbers raided the house in London Road, Worcester, at around 6.30pm last night (Saturday).
Detective Sergeant Samantha Bache said: “This was a frightening experience for the victim and a number of enquiries are now ongoing to trace those responsible.
“If anyone witnessed any suspicious behaviour in the area yesterday evening or is aware of jewellery being offered for sale in unusual circumstances, please get in touch.
“In the meantime our officers will continue to work in local communities where family gold is targeted and offer crime prevention advice to those who might fall victim to this type of crime.”
The robbers, described as white males wearing black, gloves and balaclavas, searched the property after threatening the man.
The victim was not injured.
Anyone with information can ring West Mercia Police on 101 quoting incident number 665s of December 1.