Emergency services were called to De La Warr Parade, close to the junction with Sutton Place, Bexhill shortly after 10am on Tuesday (June 1).
The collision involved a 50-year-old man riding a bicycle and a 21-year-old man riding a motorcycle, police confirmed.
Both men were taken to hospital, police said. The cyclist was taken by air ambulance with injuries including a leg injury, the ambulance service said.
Police said the cyclist is currently in a serious condition
A spokesman added: “Just after 10am on Tuesday 1 June a man aged 50 riding a cycle and a man aged 21 riding a motor-cycle collided in De La Warr Parade, Bexhill, close to the junction with Sutton Place.
“Both men have been taken to hospital for treatment, the cyclist by air ambulance.
“The cyclist, aged 50, is currently in a serious condition.
“The motorcyclist, aged 21, has also been arrested on suspicion of dangerous driving and failing to stop at the scene of a collision.
“Anyone who saw what happened is asked to contact Sussex Police at [email protected] or by calling 101, quoting Operation Ludworth.”
The road was closed while emergency services attended.
A spokesman for the ambulance service said: “We were called to reports of a collision shortly after 10am.
“Ambulance crews attended and were joined at the scene by the air ambulance service. One person has been airlifted to Royal Sussex County Hospital with injuries including a leg injury.”