Three medics were knocked down by a car while they were assisting on the scene of another accident on the R546 in Mpumalanga, ER24 said on Sunday.
"One is in a critical condition, and two others sustained moderate injuries," the paramedic service's spokesperson Ineke van Huyssteen said in a statement.
She said the most severely injured medic had to be airlifted to hospital.
The circumstance of the collision were not yet clear but police had been on the scene to investigate.
The incident, which happened on Saturday night, involved members of the ER24 Secunda team.
"Our thoughts and prayers are with them and their families during this time," added Van Huyssteen.