The card is offered after activating an iPhone 5 with Verizon, AT&T or Sprint on a 2-year plan.
In most cases, in-store customers get their gift card immediately, while online buyers should receive their gift card by mail within 3 to 5 days.
The offer is available until December 15th.
A similar deal is provided by Target and Radio Shack, with each giving away a $20 gift card with the purchase of an iPhone 5.
Best Buy offers the iPhone 5 for a full subsidized price of $199.99 for the 16GB model on contract.