Revenue grew by just shy of 40 percent year-over-year to $6.83 billion.
Wall Street was expecting at least $6.95 billion.
Dubbed itself as the nation's "Uncarrier," the company added a total of 1.65 million customers during the December holiday season, an increase from 1 million in the third quarter. For the end of year, it had totaled 4.4 million new customers.
In total, T-Mobile now serves 46.7 million customers. Total smartphone sales reached 6.2 million units.
While T-Mobile may be the darling child of the cellular industry, it's costing the firm dearly, as higher expenses offset growth in revenue and new customers.
T-Mobile chief executive John Legere said the results show "we have our strategy right," in prepared remarks on Tuesday.
"Customers are fed up with the old ways and are voting in favor of choice, innovation and doing business with a company that cares about them and is willing to earn their business. For shareholders, we transformed the company into a fierce, growing competitor that is changing the wireless industry and creating significant value."
Indeed, the company has shaken up the wireless industry, not least by cutting international data costs, killing contracts, and bi-annual upgrades for phones.