El-Erian serves as chief economic adviser at Allianz. He previously served as co-CEO at Pimco from 2007 to 2014.
He will join the Under Armour board on Oct. 1.
"We're excited to welcome Mohamed to our board," said Under Armour CEO Kevin Plank in a press release on Monday, Aug. 6. "Mohamed's renowned international, macroeconomic and financial expertise are welcomed strengths as we lean even more deeply into our transformation, driving greater operational excellence, financial discipline and shareholder returns as we continue to drive our brand forward around the world."
Under Armour last week said apparel revenue in the second quarter rose 10% to $747 million, and attributed the strength to training and running gear. Footwear was up 15% to $271 million, also driven by running. Accessories revenue fell 14% to $106 million.
The company beat revenue estimates, but the company's outlook for the rest of the year was seen as weak by some analysts.
Under Armour was down 0.7% in trading on Monday.