Of the 2.2 million iPhones sold in the December quarter, 38 percent of those were to new customers. And 40 percent of the 6.6 million iPhones sold in all of 2012 were to customers new to the carrier.
As of the fourth quarter, Sprint had sold more than 4 million 4G LTE smartphones, including Apple's iPhone 5, which debuted in September.
Sprint sold a total of nearly 20 million smartphones in 2012. In the fourth quarter, 89 percent of postpaid handset sales were smartphones.
Sprint's high-speed 4G LTE network, compatible with both the iPhone 5 and Apple's latest iPads, is now available in a total of 58 cities. The carrier expects to expand to nearly 170 more in the coming months, and construction has started in more than 450 cities.
For the quarter, Sprint reported a net loss of $1.3 billion. Dan Hesse, the company's chief executive, attributed part of that loss to subsidies associated with Apple's iPhone, which he said is one of the company's "key investments."
The 2.2 million iPhones sold by Sprint are an increase from the 1.5 million the carrier had activated over the last three consecutive quarters. The carrier had surpassed 1 million LTE smartphones just before the launch of the iPhone 5.