Robert Don, 53, suffered a serious head injury in the crash on December 30 and was taken to Ninewells Hospital in Dundee.
He remained in the intensive care unit until his death yesterday afternoon.
The collision on the A9 involved a blue and yellow single-decker coach on a scheduled journey between Inverness and Edinburgh.
It stopped immediately and the driver and 19 passengers were not injured.
Police Scotland have appealed for witnesses to the incident which happened on the southbound carriageway of the A9 between Luncarty and Inveralmond near Perth.
A spokesman said: "Officers are still trying to trace witnesses to the incident, a number of whom may have stopped to assist in the immediate aftermath."
A report will be submitted to the procurator fiscal.
Mr Don was from the Letham area of Perth. His family have said that he will be greatly missed.