Multiple police officers were seen near the Pease Pottage roundabout.
An eye-witness said the bridge was 'blocked off' and 'loads of police' were at the scene.
Sussex Police confirmed officers were called to 'reports of a man in distress' on a bridge at around 9.50am.
A spokesperson said: "Members of the public helped engage with the man and he was brought to safety and passed into the care of medical staff.
"Road closures were put in place as a precaution but all roads have now reopened."
Reports on social media suggested there was no access onto the A23 southbound, with all traffic diverted northbound.
According to traffic reports, there were also delays on M23 Southbound at Gatwick Airport, caused by an earlier stalled van.
Traffic was reportedly held in all four lanes to allow the traffic officers move the van from lane one onto a safe area. All lanes have since been reopened.