Ella Toone's first-half rocket, plus maiden goals for the club by substitutes Maria Thorisdottir and Martha Thomas, secured all three points from an entertaining WSL game staged at King Power Stadium.
Leicester's only goal also came with a United connection, as it was headed home by Abbie McManus - one of three ex-Reds in action for the Foxes, the others being Jess Sigsworth and Charlie Devlin.
If the newly promoted hosts were expected to race out of the blocks with enthusiasm, it was quite the opposite as the Reds sought to provide an early reminder of the level Leicester now find themselves at.