Armed officers responded to a report of a robbery which occurred close to Durrington railway station around 7.30pm on Sunday 3 July.
Two 17-year-old boys had personal items including mobile phones stolen, and they sustained facial injuries.
Following a search of the area, assisted by the National Police Air Service helicopter, police located and arrested two people in the vicinity of Rowlands Road, Worthing.
Two 17-year-old boys, arrested on suspicion of robbery, remain in police custody at this stage and our enquiries are ongoing.
Anyone who saw what happened is asked to report it online or call 101, quoting serial 1239 of 03/07.
You can also contact the independent charity Crimestoppers anonymously on 0800 555 111 or report it online.