Following successes over Crystal Palace and Burnley, in the Women's FA Cup, Lewes visited Farley Way Stadium for City's 14th league matchday in 2019/20.
Annabel Blanchard and Ella Rutherford were both denied by the visiting goalkeeper early on for the Foxes, while Charlie Devlin looped an effort over the bar after the break.
Ash Plumbtre, meanwhile, also forced a smart save before Blanchard's follow-up effort was blocked as Leicester pushed for an opener in Quorn.
It finally came in the 65th minute, however, as she took down a high ball and found the back of the net, via the post, to give the home side a reward for their dominant display.
The result leaves City sixth in the FA Women's Championship, with four wins and two draws from 14 games, one point behind London Bees in fifth place.
Next up, Leicester host Reading in the fifth round of the Women's FA Cup on Sunday 16 February (2pm kick-off) before staging Charlton in the league on Sunday 23 February (2pm kick-off).
The details...
City: Lambourne, Johnson, Morgan (c), Devlin, Blanchard (Everett 90'), Paul, James, Thomas (Brown 60'), Bailey-Gayle (Smith 82'), Rutherford, Plumbtre
Subs not used: Field, Cataldo, Lawrence
Goal: Blanchard 65'