In the three months through to December 31, UA reported a net loss of US$87.9mln, or 20 US cents a share, compared to earnings of US$103.2mln, or 23 US cents a share, in the year-ago period.
Adjusting for a one-time charge from the new US tax reforms, the company had breakeven earnings per share - in line with what Wall Street analysts had expected.
The big beat was with revenues though, which came in at US$1.4bn for the quarter. That was 5% higher than what UA posted this time last year and ahead of consensus estimates of US$1.3bn.
“After years of rapid growth and building a globally recognized brand, the dynamic landscape of 2017 was a catalyst for us to begin strategically transforming Under Armour into an operationally excellent company," said chairman and chief executive Kevin Plank.
The performance caps a decent turnaround for the Washington DC-based group, which saw its stock drop to eight-year lows in October as it blamed a “difficult backdrop” in its core North America market for flagging sales.
UA has had to rethink its strategy in recent months as it moves from a fast-growing business to a more mature one, competing against some big names in a tough field.
It unveiled a restructuring plan last August, for which it recognised a pre-tax cost of US$37mln in the fourth quarter.
The company added that it expects to book another US$110-130mln in restructuring charges this year after identifying further measures.
But it should pay off next year, with Under Armour forecasting “a minimum” of US$75mln in annual savings as a result from 2019 onwards.
As for this year, Under Armour is expecting revenue to rise at a “low single-digit percentage” rate, and for adjusted EPS to range from 14 US cents to 19 US cents. The current FactSet consensus is for 2018 EPS of 21 US cents.
Shares jumped 8.3% to US$14.27 in pre-market trading on Tuesday.