Run the attached example and observe what happens after the icon is set for an item. Basically it looks like item's geometry is being recalculated but no all properties are being taken into account (e.g. grid size). The item text was elided before and is not after. Resizing the window fixes all the layout, but calls to update(), updateGeometry() doesn't help (tried to call that on QListWidget, didn't try on its viewport).