Missing People UK has issued the appeal in a fresh bid to locate Andrew who was last seen on September 14, 2007.
A spokesman said: “Today marks 12 years since Andrew Gosden went missing from Doncaster. Andrew, if you're reading this, we're here for you.”
Andrew was 14 years old when he was last seen at Kings Cross station, London later that day.
He has been urged to get in touch by calling or texting 116 000. Anyone with information can contact the same number.
On the day of his disappearance, withdrew £200 from his bank account and bought a one-way ticket to London from Doncaster.
The McAuley Catholic High School student did not go to school on the day he disappeared, leaving home in his uniform, but returning home to change into casual clothes after his family had left the address in Balby before then catching a train to London.
CCTV showed him leaving the main entrance of King's Cross station at 11:25 am on 14 September 2007. This was the last confirmed sighting of him.
Speaking in 2009, his father Kevin Gosden speculated on the reason for Andrew's disappearance: "Did he decide to do the Reginald Perrin thing and reinvent himself or was there something troubling him that he felt he couldn't tell us? In my heart I still think his disappearance was a spur of the moment thing."