Emergency services were called to the scene between Cardigan and Tanygroes shortly after 12:00 BST.
A Welsh Ambulance Services spokeswoman confirmed that one person was treated at the roadside, but could not give details of the injuries.
A Mid and West Wales Fire Services spokeswoman said the road is closed for investigation work to take place.
A section of the A487 is closed in Ceredigion following a crash involving a car and a motorcycle.