A contractor was rushed to hospital after he was hurt at Sheerness Docks.
South East Coast Ambulance Service was called at 3.10pm yesterday and sent two ambulance crews.
The air ambulance also landed at the scene.
Its paramedics treated the man on the ground before he was taken to Medway Maritime Hospital, Gillingham, as a priority.
It is believed the 44-year-old had been struck by the arm of a piece of construction equipment and suffered injuries to his chest.
A spokesman for Peel Ports, which runs Sheerness Docks, said: "We are currently carrying out an investigation into the incident."