 <p>From the <a href="http://doc.qt.digia.com/qt/qsortfilterproxymodel.html#filterRegExp-prop"><code>filterRegExp</code></a> property docs:</p> <blockquote> <p>If no <code>QRegExp</code> or an empty string is set, everything in the source model will be accepted.</p> </blockquote> <p>So the "proper" way of clearing the filter is to pass an empty string rather than a match-all regex.</p>