The crash happened on the Belfast Road in Newtownards.
The tractor towing a trailer collided with a 15-passenger bus on Monday afternoon.
One passenger, believed to be in a serious condition travelling on the bus was rushed to Ulster Hospital for treatment of their injuries.
According to Belfast Telegraph, the incident happened at 4.10pm.
Police are appealing for witnesses to the crash.
See More: Northern Ireland, PSNI, Police
