Police rescue officers followed him on to the bridge, but it was difficult to reach him because he kept moving, police said.

Officers closed and reopened lanes on the bridge as the man moved around the structure, so traffic conditions changed regularly.

The closures caused massive traffic delays across all city approaches during the morning's peak.

The man was seen wearing a tracksuit, a cap and fingerless gloves. He climbed into a box on the bridge and at one stage appeared to be shouting at police officers below.

He was arrested on the bridge framework just before 10am.

All lanes across the bridge were reopened and traffic had returned to normal by 11am, but there were heavy delays across the city during the police operation.

Shortly before his arrest, the man climbed out of the box where he had been sheltering and yelled down towards the police on the road: "Get out of the f---ing car!"

He then moved towards two police rescue officers on the bridge structure and was arrested. Two Special Operations Team paramedics had also climbed the bridge to help police.

The man was handcuffed and led down to the bridge's elevator. At the bottom, he was put on a stretcher and put into the back of a waiting ambulance.

He was assessed at the scene by paramedics before being taken to St Vincent's Hospital for further assessment, an ambulance spokesman said.

Superintendent Michael Fitzgerald said traffic lanes on the bridge had been closed, "not only for the safety of that individual but for the safety of the travelling public".

"It was incredibly dangerous. I was seriously concerned for the travelling public, travelling underneath him. I did not want him to fall and come into contact with an innocent member of the public travelling beneath him," he said.

Superintendent Fitzgerald said "significant charges" would be laid against the man once a mental health assessment was completed.

“Today's operation was very sensitive, demanding a great deal of police resources.

“The scenario was constantly changing, and police responded to these changes quickly and efficiently.

“We worked as hard as possible to get this resolved peacefully without injury and we appreciate the co-operation of all agencies involved.

“We also thank the media who have been sensitive to the man's situation in their reporting of the incident,” he said.

He said police would review bridge security with the Roads and Maritime Services.

Traffic delayed

Earlier, citybound traffic was significantly delayed with traffic queued on the M2 back to North Epping, on Victoria Road past Ryde, and the City-West Link past Haberfield.

Traffic was also heavy on the Eastern Distributor, Southern Cross Drive and General Holmes Drive.

The Cahill Expressway was closed northbound, and traffic was being diverted into the Harbour Tunnel, the spokeswoman said.

Citybound traffic was reduced to a 40km/h speed limit.

The North Shore Line, Northern Line and Western Line trains across the bridge were unaffected by the police operation.

Buses travelling across the bridge had been delayed by up to 70 minutes, and there were also delays for buses on Victoria Road, the Anzac Bridge and the Western Distributor.

Some buses travelling towards the city from the north shore were terminating at north shore stations so passengers could catch trains into the city, the TMC spokeswoman said, but following the conclusion of the police operation buses were returning to their normal routes.

The pedestrian footpaths and bike lane on the Harbour Bridge remained open throughout the operation, the TMC spokeswoman said.

Support is available for those who may be distressed by phoning Lifeline 13 11 14; Mensline 1300 789 978; Kids Helpline 1800 551 800; beyondblue 1300 224 636.

With AAP