At around 5pm on Wednesday (17/8), a group of seven-to-10 teenagers approached two boys aged 12 and 14 in Vale Park, near to Aqua Vale.
Some of the boys in the group started to punch and kick the 14-year-old boy before he ran away and dropped his iPhone, which the other boy then picked up.
The offenders then attacked the other victim and demanded the phone from him before smashing it on the floor.
A 14-year-old boy from Aylesbury has been arrested on suspicion of robbery and been released under investigation.
However, police are still looking for information surrounding the incident.
Investigating officer Detective Sergeant Thomas Booth, based at Aylesbury police station, said: “I am appealing for any witnesses to this incident to please come forward.
“Also, if you have any CCTV footage in the area or any dash-cam footage if you were driving in the area around the time, I’d also ask that you check any recordings in case it has captured something that could assist our investigation.
“We have created a dedicated portal for you to upload footage to, which you can access here.
“To contact us, call 101 or make a report on our website, quoting reference number 43220368620.
“Alternatively, you can provide information anonymously to independent charity Crimestoppers by calling 0800 555 111 or via its website.”