Leap, which caters to cost conscious customers who don't want to sign a contract, said it added 29,000 customers in the quarter compared with the average expectation for 38,000 from seven analysts contacted by Reuters.
The company's loss widened to $65.2 million, or 85 cents per share, from $18.2 million, or 24 cents per share, in the year-ago quarter. Revenue rose to $760.5 million from $667.3 million.
Leap shares have lost 20 percent of their value in the last two days as bigger rival MetroPCS Communications Inc
The company's shares, which closed at $10.04 on Wednesday on Nasdaq, were trading down 5 percent at $9.51 after-market.
(Reporting by Sinead Carew in New York and Himank Sharma in Bangalore; Editing by Roshni Menon)