A two-vehicle collision happened shortly after 2pm at the Shilbottle crossroads, south of Alnwick.
The southbound carriageway was closed for around 90 minutes but has now reopened.
Emergency services, including North East Ambulance Service (NEAS), Northumbria Police and Northumberland Fire and Rescue Service (NFRS), attended.
A Northumbria Police spokesperson said: “Shortly after 2.05pm, we were alerted to a report of two vehicle collision on the A1 southbound near the Longframlington junction.
“Passengers from both vehicles required medical assistance.
“Emergency crews remain at the scene.”