The body of Steven Brown, 35, was discovered on ground near Elphinstone in Tranent, East Lothian, on February 21, 1999.
Police said they are determined to get justice for the father of three and will re-interview key witnesses, speak to local residents and revisit some sites.
Detective Inspector Gary Boyd from Lothian and Borders Police said the reason the case is being re-examined now is that people's "personal circumstances and loyalties" might have changed and they may be in a position to help the investigation.
Crimestoppers has offered a £5000 reward for information leading to a conviction.
Mr Brown's brothers – Colin, 57, William, 48, and Kenneth, 56 – said in a statement issued by police: "No-one has ever been brought to justice for this crime, and it is great to see police have not given up on finding those responsible.
"Steven's murder affected the lives of a lot of innocent people, not least his family.
"Steven had three daughters, three brothers, a sister, and a mother and a father, and we all deserve to see justice done.
"It has been a difficult time for the family, knowing there are those in the local community who know what happened to Steven that night.
"It would be a great comfort to us to see the culprits finally convicted and give our family the closure we so desperately need.
"We are appealing to people in Tranent who have information regarding Steven's murder to contact the police and help us achieve justice."
In a separate statement, Steven's former partner Wilma Brown, 48, who is mother to his teenage daughter, said: "I am grateful the police have reopened this inquiry as I have been trying for years to get justice for Steven and for people to tell the truth about his murder.
"Steven never had the opportunity to get to know his daughter, and he never will. He also raised my own son as his own.
"We would ask people to come forward and tell the truth now, and help us put his memory to rest."
Witnesses at the time of the murder reported hearing a disturbance in nearby Kerr Road in Tranent around midnight the previous evening.
A large group of men and women are thought to have been involved and it is believed Mr Brown was attacked during the incident.
Mr Boyd said: "It is now almost 14 years since Steven Brown was murdered and we are determined to bring those responsible to justice.
"We firmly believe the key to solving his murder lies in the local community, and we are appealing directly to anyone with information to come forward.
"We understand people may have previously been reluctant to approach police with any information they had at the time of his murder. However, as time has passed, people's personal circumstances and loyalties may have changed and they may now be willing to share any information they have with us.
"We believe that, with the community's help, we can finally bring those responsible for Steven's death to justice."