If objects that "live" in different threads are connected, a queued connection will be created, by default. However an object will only be able to process queued signals, if the thread to which that object belongs, is running an event loop! That's because in contrast to a direct connection (where the slot is called directly from the emit statement and thus from the context of the thread which called the emit), with a queued signal, the event loop of the thread where the receiver object "lives" will pick up the signal and then call the slot (i.e. the slot is now called from the context of the thread where the receiver object "lives", not from the sender's thread). So if you re-implemented QThead::run(), call QThead::exec() there in order to start an event loop in that thread...