On 13 July 2018, it was announced that James would be part of the first professional Manchester United squad due to compete in the newly restructured 2018–19 FA Women's Championship.[3] She made her competitive debut for Manchester United in a 1–0 League Cup victory against Liverpool, on 19 August.[4] She scored the opening two goals in United's first game of the 2018–19 Championship season, a 12–0 win away to Aston Villa.[5] James was voted FA Women's Championship player of the month for September following her three goals across Manchester United's unbeaten opening month.[6] On 20 April 2019, James scored four goals in a 7–0 league win against Crystal Palace.[7]