A shower door assembly with at least one adjustment assembly has an adjustment device and a locking device. The locking device includes a blocking element, a pressing element and an elastic element between the blocking element and the pressing element. The elastic element is arc-shaped when unlocked. An inclined surface projects to the blocking element. The curvature of the elastic element is thus reduced until it engages with the adjustment device. A driving device includes a cam mechanism and a sliding element having one end in contact with the pressing element and the other end sliding along with the inclined surface when driven by the cam mechanism so as to push the pressing element toward the blocking element, and thus reduce the curvature of the arc-shaped elastic element until the elastic element is engaged with the adjustment device.