In January 2013, Mewis was drafted in the first round (third pick overall) of the 2013 NWSL College Draft to FC Kansas City for the inaugural season of the National Women's Soccer League.[12][13][14] She was elevated to U.S. Soccer-subsidized status during the year.[15] She scored her first goal of the season in the 74th minute of the Blues' 3–2 win over Portland Thorns FC on May 8.[16] Mewis made 20 starts as a rookie for FC Kansas City during the regular season helping the team finish second in the standings with an 11–5–6 record.[17] The team advanced to the playoffs but were defeated 3–2 in the semifinals by Portland.[18][19]