Shares dropped 3 percent in morning trading.
Nationstar's net income in the three months ended Dec. 31 rose to $63.8 million, or 71 cents per share, from $14.9 million, or 21 cents per share, a year earlier.
Revenue grew 284 percent, to $332.6 million from $118.6 million.
Much of the increase came from gains on mortgage loans that the company plans to resell. Nationstar originated far more mortgages because of a "favorable market environment."
Mortgage origination volumes have been increasing industry-wide as the housing market recovers in many parts of the country.
The results were far stronger than Wall Street had expected. Analysts surveyed by FactSet had anticipated earnings of 69 cents per share on revenue of $284.6 million.
For the year, Nationstar earned net income of $205.3 million, or $2.40 per share, on revenue of $582.0 million.
Nationstar, based in Lewisville, Texas, collects monthly payments on more than $300 billion worth of home loans. It purchases the rights to service these mortgages from banks and other companies that made the loans. Nationstar also originates mortgages.
Shares fell $1.32, or 3.2 percent, to $39.74 in morning trading.