The Saddlers had gone four games without a win, but they set about the visitors right from the start, allowing them little time on the ball and scored what proved to be the only goal of the match in the seventh minute.
Winger Sofiene Zaaboub delivered a great cross into the goalmouth where Troy Deeney headed his third goal in as many games.
Despite the fact that they still had three key players out injured, Walsall were comfortably the better side in the first half with Leeds showing little of the form which had brought them three successive victories.
In the 32nd minute Leeds' top scorer Jermaine Beckford had a half chance when he intercepted a Rhys Weston clearance, but he shot tamely straight at goalkeeper Clayton Ince.
The visitors improved in the second half, introducing three substitutes early on, and in the 59th minute Ince did well to smother a low drive from Jonathan Douglas following good work by Lee Trundle.