Robert Hutchinson, 57, was last seen leaving his home in the Hendon area of Sunderland on 23 June 2014.
His car was later found abandoned and Northumbria Police are treating his disappearance as a murder.
Crimestoppers has offered the reward for information about what happened to him.
Det Insp Ed Small said: "Our condolences very much remain with Robert's family.
"I'm sure it has been a very difficult few years and the not having the answers only prolongs their grief.
"We need answers to what happened to him.
"There will be people in the community who will have information about his murder."
He was last seen leaving his home in Corporation Road at about 18:20 BST. His car was found several days later abandoned at the end of Stewart Street, just off Chester Road.
Crimestoppers previously offered a £3,000 reward for information.
Two men were arrested but no charges were ever brought.
A £10,000 reward is being offered in the case of a man who disappeared three years ago and police believe has been murdered.