Sprint has struggled with the cost of running two disparate wireless networks as Nextel customers have cancelled in droves.
In the first quarter, Sprint's net loss was $863 million, or 29 cents per share. In the same quarter last year, the loss was $439 million, or 15 cents per share.
Analysts polled by FactSet were on average expecting a loss of 42 cents per share.
Revenue was $8.73 billion, up 5 percent from a year ago, as iPhone subscribers boosted services fees. Analysts were expecting $8.71 billion.
The Overland Park, Kan., company's shares are up 2 percent in premarket trading.