The road was closed between the A697 (Morpeth) and the A1068 (Alnwick) after a collision near Felton.
Emergency services attended.
A North East Ambulance Service spokesperson said: "We received a call at 8:45am to a three vehicle road traffic collision on the A1 north near Morpeth. We sent two ambulances and an officer to the scene. We transported two patients to hospital in Cramlington and treated a third at the scene."
National Highways posted: ‘The carriageway is clear and the #A1 northbound has reopened between the #A697 and the #A1068 near #Felton following the earlier collision. Traffic is flowing freely and residual congestion has cleared. Thank you for your patience this morning #Northumberland’.