Police are appealing for witnesses after two men walked into Wokingham Pets in Crossway then left in the direction of the High Street after they were challenged by a staff member when one of them went behind the counter.
The shop worker then realised that her Apple iPhone 4 had gone missing from under the counter.
PC Marius York from Bracknell police station said: "I would like to hear from anyone who can help identify these men, or if you saw them walking along the High Street."
The men are black, 6ft 2ins, aged 19-25 and they wore designer jeans and hooded tops.
The phone is black, serial number 012836005010338 and it has a Gucci logo in gold stamped all over the back.
It happened at 3.45pm on Thursday, August 2.
Call the 24-hour Police Enquiry Centre on 101 and ask to speak to PC York or call the charity Crimestoppers anonymously on 0800 555 111.