It is weird. But maybe you can just add QVTK or QVTKWidgetPlugin to target_link_libraries instead of -lvtkGUISupportQt-6.2. -- View this message in context: http://vtk.1045678.n5.nabble.com/VTK6-with-Qt-undefined-reference-to-QVTKWidget-tp5732148p5732178.html Sent from the VTK - Users mailing list archive at Nabble.com.