She signed with Nike to a multi-year endorsement arrangement, giving up her college eligibility in the process,[9] and joined the Portland Thorns FC academy.

[12] Although she trained with the Thorns' senior team[13] and appeared in exhibition matches, she had been prevented from signing a professional contract with the club, as the National Women's Soccer League (NWSL) prohibited players under age 18, while FIFA, soccer's international governing body, generally prohibits minors from playing overseas.

[17] The suit asked for immediate action from the court by granting a temporary restraining order against the age rule so that Moultrie can play in regular-season games during the 2021 season.

[18] On May 24, 2021, United States District Judge Karin Immergut granted a temporary restraining order, ordering the league to lift its age limit and allow Moultrie to compete for a roster spot on the Thorns, writing, the league had not "presented any compelling procompetitive reasons to justify this anticompetitive policy, nor have they shown that eliminating the Age Rule will cause any non-speculative injury to the NWSL.

"[19] In June 2021, the league informed all member teams of a discovery process for Moultrie, ultimately awarding the rights to OL Reign,[20] who subsequently traded her to the Thorns for a third-round draft pick.

[24] On August 19, 2021, Moultrie scored her first professional goal, a 57th-minute direct free kick against Houston Dash, in the semifinal of the International Champions Cup.

[34] In 2019, shortly after turning pro, Moultrie had a small role in Nike's all-women "Dream Crazier" commercial that debuted during the 92nd Academy Awards broadcast and was narrated by Serena Williams.