At 11pm on Sunday 16 November a man entered a service station in Largs Bay and threatened staff with a syringe.
At 6.30pm on Monday 17 November a man entered a deli on Fletcher Road in Peterhead where he threatened staff with a knife.
On both occasions no one was physically injured and the man fled the stores with an amount of cash.
Detectives from Western Adelaide CIB, today, arrested and charged a 17-year-old boy from Largs Bay with two counts of aggravated robbery.
He has been refused bail and is expected to appear in the Port Adelaide Youth Court tomorrow