Layton Cashmore died in hospital after suffering serious injuries in a crash at the junction of Hill Lane and Warwick Road.
The 14-year-old from Hedge End had been a passenger on a Suzuki motorcycle which crashed into a VW Golf.
Paying tribute to him, his family said: “As a family we cannot put into words how much this means.
“Layton is truly one of a kind, with the biggest heart, he left a mark on anyone who had the privilege of knowing him.
“As a family we will never be the same.”
READ MORE: Three arrested after motorbike crash in Hill Lane, Southampton
PS Jon Bates of the Highways Policing Unit is leading the investigation.
He said: “Firstly, I would like to express my condolences to Layton’s family.
“We are continuing to investigate the circumstances of what happened and are asking anyone who saw the collision or has dash cam, CCTV or doorbell footage of the incident to contact us.
“If you know who was involved in the collision, or saw a moped at the scene and know who was driving it or who was a passenger, please also get in touch.”
Contact us on 101 or inform us online, quoting 44220288681.
You can also contact the charity Crimestoppers anonymously on 0800 555 111.
Three 16-year-old boys from Southampton were arrested and released under investigation pending an investigation.
The police have now presented a call for witnesses after the events that happened around 5.20pm this Monday.
Anyone with information is asked to call 101 quoting the crime reference 44220288681.