Police were alerted to a reported dog attack at the busy train station just after 4.30pm on Sunday at Stratford Station.
Officers attended and two dogs have been taken to a secure kennel while the British Transport Police makes enquiries.
Onlookers said a man offered to hold one of a woman's two dogs so she could attach a harness to the other animal.
Footage of the incident on social media shows the man on a train platform struggling to keep a XL bully-type dog on its lead as it jumps up and tries to bite him.
He then falls to the floor by the edge of the platform as a DLR train approaches.
The man manages to kick out at the barking dog before fleeing down the platform.
The woman, who was holding back a second dog nearby, can be heard shouting "give me the dog" and "can I have it" as the attack takes place before she grabs the animal.
The British Transport Police has asked anyone with information to text 61016 or call 0800 40 50 40 quoting 422 of 10/12/23.
