It happened around 4:00 p.m. on Wednesday at the Christiana Mall in Newark, Delaware.
Police say the men followed the 17-year-old victim into the bathroom in the food court and broke into a stall. Police say they threatened the teen and took money, an iPhone and an iPod before fleeing.
The victim notified security, who found the men still in the mall. State police were called and arrested the men.
They are identified as Andre James, 20, Dominique Brooks, 18, and Christopher Moulton, 18. All three are from Wilmington.
They were charged with robbery.
The victim was not hurt.
A photo of James was not available Thursday morning.
