The athletic gear company said Sunday that it has been cooperating with the U.S. Securities and Exchange Commission and the U.S. Department of Justice on their investigations for two years.
The company said it firmly believes its accounting practices and disclosures were appropriate.
Under Armour reports earnings for the third quarter Monday.
The investigation was first reported by The Wall Street Journal, which said the probe involves whether the retailer shifted sales from quarter to quarter to make results appear stronger.
Under Armour founder Kevin Plank stepped down as CEO last month. The company has struggled since its explosive sales growth petered out in 2017. Last year it announced job cuts as part of a restructuring effort.