Police officers, paramedics and firefighters were called to the collision, involving a car and a motorbike, on Terringes Avenue at around 9am.
A Sussex Police spokesman said: “The motorcyclist was taken to hospital with serious but non-life threatening injuries.
“The road was closed for around three-and-a-half-hours while emergency services attended the scene.
“Anyone with dash cam footage or witnessed the collision is asked to contact [email protected] or call 101 quoting serial number 236 of 17/01.”
A spokesperson added: “The fire crew assisted police officers in making the scene safe and left the incident at 9.50am.
“Paramedics from SECAmb were also in attendance.”
According to traffic sources, a detour was in operation whilst the road was closed.
Slow traffic was reported between The Boulevard and Church Road.
The incident affected bus services in the area. Stagecoach South wrote on Twitter: "Due to serious RTA at the junction of Ringmer Road and Terringes Avenue, Service 10 cannot serve Ringmer Road and Castle Road."