The protest was organised by the Auckland GetAcross campaign group, in response to the New Zealand's Transport Agency's rejection of at least three proposals to allow cycling and walking on the bridge.
Last week NZTA decided not to allow the protest for safety reasons.
The group said it wanted to celebrate the bridge's 50th birthday as well as protesting the lack of cycle and pedestrian access by crossing it .
Event spokesperson Bevan Woodward told NZPA the group had not intended the crossing to take place against the wishes of police and NZTA, but they could not stop "people power."
Mr Woodward earlier told the crowd it was in NZTA regional director Wayne McDonald's hands whether they could cross.
Mr McDonald was also at the event and was heckled when he told protesters they could not cross.
Mr Woodward said he was surprised by the level of support the protest received.
Auckland Regional Transport Authority chairperson Christine Rose told the protesters the bridge needed to be open to cyclists and walkers because "we want a city that burns fat not oil."
Commuter cyclist Peter Schmiedeskamp told NZPA the bridge needed to be permanently opened to cyclists and walkers.
"It's important we all show our support to get over the bridge it's a premium section of roadway in New Zealand, if we are serious about being green, then this is an important place to make a stand ."
Protesters, including children crossed the bridge on foot and on bikes.
Police said there were no arrests or injuries during the protest.
The bridge was close to northbound traffic for about an hour between 10am and 11 am caused major delays and backups.
