A violent brawl on a Perth train has been captured on camera.

The shocking vision was captured by a passenger on a Fremantle-bound train on Saturday night.

Witnesses say the fight broke out after the man in dark clothing provoked a stranger for no reason, causing another commuter to intervene.

In the video, the man in grey can be seen approaching the man in dark clothing before punching him.

The pair began fighting in front of shocked onlookers before the man in grey performed a citizen’s arrest.

The instigator was held until officers arrived, it is understood.

PerthNow has contacted WA Police and TransPerth for comment.

The West Live producer Shannon Beven has the details.