Set column width for QTreeWidget

QHeaderView::resizeSection() should do the trick, in C++ it would look like this:

myTreeWidget->headerView()->resizeSection(0 /*column index*/, 100 /*width*/);

For people looking for a C++ Qt solution (tested with 5.12):

// Important to call setMinimumSectionSize because resizeSection wont work if your width is less than the minimum
treeWidget->header()->setMinimumSectionSize(25);
treeWidget->header()->resizeSection(1 /*column index*/, 25 /*width*/);

// You might also need to use this if you want to limit the size of your last column:
treeWidget->header()->setStretchLastSection(false);