Ms Dorrian was last seen at a party at a caravan site in Ballyhalbert on 28 February 2005.
Despite land and sea searches, her body has never been found.
The Crimestoppers charity is offering a reward for information leading to the arrest and conviction of those responsible.
Police have previously made several arrests, but no-one has been charged with the 25-year-old Bangor woman's murder.
The Dorrian family have tried a number of initiatives since she went missing, including linking up with Snow Patrol singer Gary Lightbody and releasing a short film at cinemas.
"Lisa's family have endured 10 years of pain and unanswered questions following her disappearance and they deserve to know what happened to her," Peter Stafford, Crimestoppers committee chairman for Northern Ireland, said.
"We take your information completely anonymously, never ask for any of your details, and significantly, you'll never have to give a statement to police or go to court.
"So please, do the right thing and tell us what you know and help bring some peace to this family."
The new reward is in addition to one of £10,000 previously put up by the family.
A reward of up to £5,000 has been offered for information about the suspected murder of County Down woman Lisa Dorrian.