In January 2013, Mewis was called to the national training camp by head coach Tom Sermanni in preparation for a friendly match against Scotland. She made her debut for the senior team on February 9, 2013, against Scotland and was placed on the roster for 2013 Algarve Cup. Mewis scored the game-opening goal in the third minute of a friendly match against South Korea on June 15, 2013, near her hometown in Massachusetts.
